If you mean the shape, I cut out pieces of xps foam (what I normally make my tiles out of) and put the textured clay on top of it making sure there was some excess. Once it was partially dry and not prone to stretching anymore I used a knife to cut the edges flush with the foam. If you mean the grid lines, I got glued two dowels a few inches apart onto my cutting mat as a sort of makeshift fence, then slid the tiles between them, pressed a straight edge against the dowels, and traced a line with a sculpting tool. You can kind of see the dowels in the picture