Hollandaise broke mid rush and you saved it? Show off.

So you found a rock that looks like someone tried to make a Minecraft block out of it? Ok but real talk, flint that comes out square with chipped edges is actually pretty common in certain creek beds around here because the stuff breaks along flat planes, so you get these blocky chunks that look worked when they're not. The flat spot you're talking about could be a strike platform from someone knocking flakes off, which would make it a core, or it could just be a natural fracture that happens to look right. Here's what I'd check: look for little ripples or a bulb shape near that flat spot, because a real strike leaves a bulge and ripple marks in the stone, while a natural break usually looks dull and flat. Also run your finger along the edges, worked edges feel zigzaggy and sharp in a repeating pattern, natural ones are more random and worn. Two inches square is a weird size for a core though, most knappers work those down smaller, so I'd lean toward geofact unless you see clear flake scars running in one direction.