Here are some pictures of what I did.
I basically measured the inside of the bin where I wanted the level to go. Then I cut the wood according to the measurements of the bin. Then I found these pieces of wood that we're 1x1 and about 2 or 3 feet long. Home Depot calles it a poplar square dowel. So I took that and measured the height that I wanted and cut four legs. In my case I cut 4 pieces of wood at 7 inches each. Then I got some screws and screwed them to the corner of the wood top. Like a table!
My new hamster thought it would be fun to chew on one of the legs but after giving her toys she's stopped. So I would suggest cutting extra legs in case they get chewed or peed on. As for the top part of the level, it hasn't been peed on yet. Just the legs since they are in a corner. If this happens you can place a litter box in that corner and that should solve the problem.
I've had these levels for 11 months and it's not until now that I've had to replace 2 legs. One from Kit Kat peeing on it. She refused to use a litter box. Second leg was because Aria thought it would be funny to chew on it.
I use poplar wood. I stay away from anything else. :/