Amazon You use a glass cutter to cut a glass into any shape you want. It sounds impossible but it's actually quite easy once you get the hang of it. The glass I was using was thin because if it's too thick, cutting it could be a challenge. You usually run your cutter in a straight line, but once you are used to it, you can do irregular shapes such as a circle. As mentioned in the previous section, if you are planning to slump your product in some mold, you need to cut your glass the same shape as that of the mold.