3. Measure and Cut Support Pieces
Use your leftover cardboard strips to build an X, or a frame, or random strips. These will help your tombstone have the support it needs throughout its midsection.
Even if you’re accustomed to fudging it, you’ll need to measure how deep you’ve made the stones. Use that attached bottom piece you cut, so the supports will fit inside. Otherwise, you’re going to have an oddly pregnant stone.
Tape the supports to the inside of one of the stones before assembly.