You can have them milled and V-grooved in a similar way to the way it is done on FR4 PCBs.
The edges where they are separated from where the V-groove was will not be smooth, the other edges will be smooth.
If you require all the edges to be smooth you can have them milled out entirely and insert them into carriers for assembly.
Read More: A Must Read: PCB Material Guide
#PCB Assembly #PCB Materials