What you need:
1. Foam insulation 4x8 sheet - Home center. I used the white foam but the blue or pink foam works also.
2. Tape measure
3. Sand paper
4. Razor knife with a really long blade
5. String - or string substitute (I used headphones)
7. Spray glue - make sure it is foam safe - craft store
Step 1: Cut out shape
Cut the foam into rectangles the size you want your tombstones to be.
Now grab your string and stretch it across your foam. Now fold your string in half. Where the string bends is the center of the foam.
Grab you marker and hold it in one hand with one end of the string and stretch the string out to the bend, to the center of the foam. Keep that hand there and with your maker hand draw a semicircle at the top of your tombstone. Then cut along the line to make your tombstone shape.
After that, trace that tombstone twice and cut out. You want three identical tombstones.
Now sand the edges to get rid of jagged cuts.