I don't think you really need to build a "frame" per say as you would for a wall. All I did for mine was take 4 2x4's and drill them to the floor, cut a peice of plywood or whatever you are using as a bottom and sides, get a few 90 degree corner braces and put the sides and drill it together then put the top and dividers on. Below is a pic of mine. Hope it helps alittle.
This is the picture of the 90 degree brace.

This is the picture of the 90 degree brace.
