A few years ago I decided I needed a way to display my ponies so I could actually see them all. I was tired of messing with dozens of boxes as makeshift risers and I couldn't afford nice acrylic risers so I decided to make my own.
Here's how I did it
Two sheets of 20"x30"x3/16" foam board
Hot glue gun with several glue sticks
Yard stick, T-square or some other kind of straight edge
1 Yard of felt (optional)
First you need to cut out your side and middle pieces. I made a stencil so I can just trace around it instead of measuring it out every time. You could use the back side of a cereal box, store bought pizza box or something similar to make your stencil should you want one. The measurements will depend on the space where you display your ponies but I'll include the measurements I use for my risers in just a bit to give you an idea of the proportions
My risers were cut to accommodate mostly G1 and G3 ponies so if you're only displaying G4s or babies you could work in an extra level on your risers and have even more room. It all depends on what you're displaying and where you're displaying it. Make a few test patterns on regular paper and hold them up to the spot you intend to put them to make sure of the fit. Also hold ponies up to them to make sure the steps are the right height for the look you want to achieve.
Please post your results in this thread if you make these risers, I'd love to see what you come up with!