Step 1: Materials
4x 12-1/4" (this dimension can be varied if you want it to be longer)
36x tee connectors
16x 45 degree connectors
1x cross connector
10x safety pins
(optional) miter box
(optional) file (highly recommended)
Step 2: Cutting the pipe
Cut the pipe with the hack saw, using the miter box to help easily make a straight cut. Applying some beeswax to the back of the blade will help it go through like butter.
After you cut, file the ends of the pipe to smooth the rough edge. This is "optional", but connecting the pipes and connectors is a lot easier with a smooth end. You can use a regular file, or there is a tool made especially for filing the ends of PVC.
Step 3: Build four corner walls
Add a 3" piece of pipe to the open end of each of the four T connectors. Then add a 45 degree connector to these.
Repeat four times to make four walls.