Use a 2mm and 3mm drills or rods to suspend the plastic block. Insert four m3 bolts to secure the lid. Use a syringe with mixed 2 component heat resistant silicone to fill the mold. While filling, close the "venting" openings with tape or a screw, use your imagination. The silicone will leak out if not closed up properly. The silicone will not stick to the mold, if you used the correct silicone... After hardening, remove the rods and bolts, and gently coax the sock out of the mold. DON'T FORGET TO PERFORM A NEW PID AUTOTUNE ON THE HEATER! The sock thermally isolates the heater, this will result in different heating characteristics...