The styrofoam trays of pizza's can also be used as stamps. With an empty ballpoint I pressed circles into a pizza tray. By pressing the styrofoam compresses a bit and creates a slight heigt difference. The tray is thin, so I needed something like a handle to lift it from the fabric. For this I folded a piece of cellotape partly double and pressed this to the back of the tray.
I placed my fabric on the printing board and applied the paint with a foam roller. I pressed the tray onto the fabric and repeated this. This is the result: