Yes, you can use frozen strawberries but I highly recommend using fresh ones. Frozen strawberries hold extra water that will seep into the dough making it wet, sticky, and harder to work with. You may also find that the dough changes color (not necessarily a bad thing just something to be aware of). Here’s what I would do. Cut the frozen strawberries into small pieces and add them to the dough. Now try to assemble the cookies as quickly as you can. Hope that helps.