Finally got materials - have some questions before building.

1, Use 5 to 6 cable ties ber grid connection if your not using connectores 2. It is more common to be put on the inside, that way you don't have to clean the bottom of the grids. 3 Yes it is fine, just make sure it is centered, 4 YOu can add it later, or when you start, it really doesn't matter. 5 I'm not sure, sorry. 6. Make sure your lines are straight before cutting . Remember, Measure twice, cut once.

First, the connectors that came with my cubes are a pain to use, so how many cable ties does it take per connection to be stable?

I use three, one on each end, one in the middle.

Second, is it better to put the coroplast box inside or outside of the grids?

If you want it to overhand on the table by more than 1.5''-2'' on each side (needs to be an even overhang on each side if over one inch), put the grids on the inside. Otherwise, outside works and is easier to clean.

Third, is it okay for it to overhang the table a little bit?

If it is perfectly stable, and the grids are inside the coroplast if it is a large overhang.

Fourth, do I have to put in the upper level right at the initial building or can I wait until I've had it all set up for a week or two to add it?

That is fine.

Fifth, how the heck do I cut the coroplast to make an L-shaped cage [I have two sheets of it]?

I would suggest making two peices and connecting it with tape. Seems to work better for me.

Sixth, anything else I should know before beginning.

Dag is right, measure twice, cut once. If the coro is going on the outside of the grids, add an inch. If it is going outside, deduct an inch. (Connectors take up about .5'' each.)

Remember to follow: https://guineapigcages.com/howto.htm

Yeah, slap is right, I was thinking about making door with cable ties, three would deffinatly be enough.