You can use some kind of steel bed (devcon) and make pillars this way. Drill out the action screw holes to about 1/2 inch. get some 20 mill PVC tape and wrap your screws. Fill all holes with clay that you don't want any bedding compound to get into including the inletting for the bottom metal. Wax or spray with a release agent the screws and receiver and any matal part that will contact the bedding compound.

Put the screws into the holes and fill with the steel bedding compound from the top and bottom making sure that there are no air bubbles and use enough so that there is more than you need filling the holes. Drop in the receiver and screw inthe screws. Clamp the receiver to the stock wipe off any excess that is oozing out onto the bottom metal inletting and let dry over night. Remove the screws and scrape away any excess bedding compound.