Here the mold has been layed up with fiberglass, the o-ring channel has been inserted, and a strip of stainless steel has been inserted as backing for hinges. Also note that the whole assembly is resting in a box. This was done so that a jig could be clamped to the top edges of the box. This jig has strips of MDF on it that were tied directly to the o-ring channel with monofilament line, to ensure the the o-ring channel was positioned exactly flat, with respect to the top of the lid. The monofilament line was then simply cut to remove the jig once the epoxy was cured. Sorry I neglected to photograph this step.

Here the mold has been layed up with fiberglass, the o-ring channel has been inserted, and a strip of stainless steel has been inserted as backing for hinges. Also note that the whole assembly is resting in a box. This was done so that a jig could be clamped to the top edges of the box. This jig has strips of MDF on it that were tied directly to the o-ring channel with monofilament line, to ensure the the o-ring channel was positioned exactly flat, with respect to the top of the lid. The monofilament line was then simply cut to remove the jig once the epoxy was cured. Sorry I neglected to photograph this step.