With silicone foundation molds, a common practice is to apply a release solution to the mold before the wax.
A few years ago the Herring wax foundation mold was marketed. It was 2 sheets of impressed hard silicon joined along the top edge. The beek had a session making sheets of thin plain wax. A sheet of wax was placed between the silicone plates. The parcel was then run through a mangle (wringer). The impressed sheet of wax was later cut to size and wired. All this took time and labour.
I don't know anyone who makes their own wax foundation now but there will be someone. A Herring kit in last years bee equipment auction went for peanuts.
For additional info ........ Do a search for "Herring" on the Dave Cushman site........ dave-cushman.net
Hope this helps.