Print with temperature resistant materials. This tool needs to withstand temperatures ~80°C. Depending on the model, you may need M6 screws and nuts OR magnets. You can use the tray models to collect the leakage. Usually, the leakage is negligible.

Before curing:
Assemble the device, add the PDMS, degas and incubate at ~85°C.

After curing:
If you are using the tray, carefully peel off the tray from the bottom.
If you are using screws and bolts, remove those first.
Carefully, peel off the wall(s) from the ground plate.
Carefully, insert a blade between silicon wafer and the ground plate and cut around the sides up to 2-3cm deep. This should make is easy to detach the wafer from the ground plate by hand without breaking it.
Then you can peel off the PDMS from the wafer.