Here's how to make a really inexpensive ooth hatchery/nymph cage in 15 minutes plus the time that it takes for the glue to dry.
Get a plastic container that kitty litter is sold in. If, like me, you don't have cats, get one from someone who does. Use a ruler to draw a square hole in the top and two opposing sides (just one side if you're feeling lazy), leaving enough plastic to glue the mesh in place.
Use a utility knife -- you've got to have one lying around somewhere -- to make check cuts at each corner, and then cut the marked square out of the lid and then the sides.
Cut plastic window screen into squares large enough to glue over the three (or two) holes, using hot glue or five-minute epoxy. Start by gluing one edge in place over each hole. Once the glue has set, pull the opposite side tight and glue it. Then, when that is dry, glue the other two sides of the screening. If you glue all four sides in place at the same time, it is very hard to keep the screen mesh taut.
Finally, bore/cut a 1" hole in one of the remaining plastic sides, as you would in a deli cup and stop it with a bung. This is your ff feeding hole.
When you have to clean out the cage, periodically, just leave on its side for a few hours with one mesh side up. The nymphs will move to it, making the lid removal easy. I am too impatient to do this, usually, and instead, I remove the lid, nymphs and all, and put it on another, empty container while I work on the dirty one. I made these before I got mesh cubes, but they are nice to have around. If you want something slightly fancier, cut a square hole in a third side and cover it with a piece of 1/16th or thicker clear plastic. Maybe I'll dig one out, later, and take a pic.