Flat-earth proponents tell us the Hebrew word chug (חוּג, pronounced "khoog") means a "flat, circular disk," that Isaiah 40:22 shows God enthroned above that disk, and that Isaiah would have used a different word if he had meant a ball. It sounds technical and plausible, as if based on the work of someone who has actually read Hebrew, but sounding "technical and plausible" doesn't make the claim true.
Chug is only used 4 times in the Bible, so we probably shouldn't be dogmatic about the limits of its meaning. The only thing that everyone seems to agree on is that it refers to something circular. Whether that can be a ball or a disk or only a hollow circle is debatable. However, we can learn a lot from the context of those 4 verses.
The Verses
Thick clouds veil him, so that he does not see, and he walks on the vault [chug] of heaven.
Job 22:14 ESV
In this verse, Eliphaz is accusing Job of thinking God is too far away to notice human behavior. God is behind the clouds, so he can't see what we do, and he walks on the chug of heaven (chug shamayim).
Several things follow from the context. The chug belongs to heaven, above or among the clouds, because the clouds are what hide God from our view and us from his. It is also something a person can imagine God walking on, which would imply a solid surface if we didn't already know that God can walk on water.
The verse doesn't tell us whether the chug is solid, how thick it is, or how it is shaped beyond being a circuit or arch above our heads. This is Eliphaz's caricature of Job's supposed view of God, and not meant to be a reliable description of anything. For all we know, Job held to a completely errant cosmology or Eliphaz misunderstood Job's views (more likely, since he claimed Job doesn't believe God can see what humans do). Eliphaz doesn't give any other details about this circle. He doesn't mention a firmament or God's throne room, and doesn't imply anything at all about the shape of either the heavens or the earth beyond their relative directions.
Whatever the word means here, it doesn't refer to the earth. It is a circle or arch or pathway of heaven, which might even be intended as a metaphorical description, not a literal description of a physical place.
He has inscribed [choq] a circle [chug] on the face of the waters at the boundary between light and darkness.
Job 26:10 ESV
Job is replying to Bildad who seems to have applied a Calvinist-like view of Utter Depravity to the entire world. In Job's view--not necessarily God's--the circle (chug) is something God draws on the surface of the waters, presumably the sea since the boundary between light and dark isn't likely to be seen on a river or lake.
Speaking from his own perspective, Job describes a line that divides light from darkness or at least marks the boundary between the two. I think Job could be describing one of three things:
1. The solar terminator where sunlight is blocked by the curvature of the earth. This is a perpetual circle around the entire earth dividing the dark side from the light. It moves across the surface as the earth rotates, creating the day/night cycle.
2. The edge of a disk-shaped earth that is ringed by oceans. This would seem to preclude the ice wall that most flat-earthers claim rings the earth to hold in the seas. I'm sure that Job understood that ice is frozen water, but he uses a different word for ice in 6:16. Elihu uses that same word for ice in 37:10, and God himself does in 38:29. Job didn't describe a circle on "the face of the ice wall" in 26:10, but on the face of the waters.
3. The visible horizon where the daylit sky seems to touch the dark surface of the sea. Since the depths of the seas and darkness are thematically linked throughout Scripture, and Job was perfectly capable of observing the horizon over the seas, I think this is the most likely meaning.
The verse says nothing about the shape of the earth itself, only that God made a circle or arc on the surface of the water to divide light from dark.
When he established the heavens, I was there; when he drew a circle on the face of the deep...
Proverbs 8:27 ESV
This passage is a personified Wisdom establishing her authority as a companion and helper of God from before the creation of the physical world and instructing the reader to value and seek out wisdom for himself.
The Hebrew uses a verb (chaqaq) with the same root as used for "inscribed" in Job 26:10 (choq) and the same phrase "on the face of" with a body of water. In Job it is the face of the waters, and here it is the face of the deep, but I think they are meant to convey the same meaning of the deep darkness of the seas.
Although she and Job both describe real actions by God, their language is clearly poetic and meant to convey information about God and Wisdom, not necessarily about the structure of the universe. I think the same three possible meanings of chug from Job 26:10 apply here, and the verse says nothing about the shape of the earth itself, only that God made a circle or arc on the surface of the sea.
It is he who sits above the circle of the earth, and its inhabitants are like grasshoppers; who stretches out the heavens like a curtain, and spreads them like a tent to dwell in.
Isaiah 40:22 ESV
This is the only one of these four verses where the chug belongs to the earth (chug ha'aretz), as opposed to the heavens or the sea. The context is God looking down on his creation. God sits above the chug, and from there he stretches out the heavens and the inhabitants look like grasshoppers. The text isn't trying to describe the structure of the universe--let alone the earth--but to describe God's supremacy over his creation. The question is whether or not the verse uses a literal description of the earth to make its actual point.
Isaiah doesn't say "above the circular earth" or "above the global earth", but "above the circle of the earth". He only talks about a circle, which could be either a disk, a sphere, or a single line. It's even possible that "circle of the earth" doesn't refer to the outlines of the earth at all, but to some smaller part of the earth (remember that erets also means land), in which case the earth could be any shape at all and still have a circle which God could see from above.
The Bottom Line
Math, experimentation, and direct observation by an objective person all prove that the earth is a globe, but there is nothing in any of these verses that requires any particular shape of the earth. A cube earth fits just as well as a globe or a disk. None of these passages mentions an edge, an ice wall, an underside, or corners. One might object that the contexts of Proverbs 8 and Isaiah 40 strengthen the disk-earth interpretation when they mention "foundations", but that also works with any shape. Globe-earth proponents can speak of the foundations of the earth just as well as disk-earth proponents and everyone knows exactly what they mean. The disk and the globe both have to be inserted into these passages by the reader because it is missing from the text.
Chug denotes a circle, an arc, or a circuit of the heavens, on the sea, and of the earth. By itself, it asserts nothing about the shape of the earth. Reading it as "flat disk" imports a model into the verse, and neither the Hebrew nor the context requires it. If you want a flat earth, you'll have to bring it with you. The Hebrew didn't pack one.
