What you need.
1. Foam 4x8 sheet, the thicker the better - Home center
2. Knife with a long blade
3. Latex Paint - Craft store
4. Spray glue - Test to make sure it doesnt dissolve the foam - craft store
5. Wooden dowel - Craft store or home center
6. Plaster - Home center
Step 1: Cut n Glue
Now glue 2 2x2 pieces together with spray glue then repeat. Then glue 2 2x6 pieces together and repeat.