I am working on a table-building project involving a walnut slab that has a number of defects (knotholes, etc.) that I would like to fill with clear epoxy prior to sanding flush and applying a rub-on polyurethane finish. Many of the resins available have a yellow or amber cast when poured to any thickness, which would be undesirable. The slab is approximately 3″ thick and some of the defects go completely through the slab, so would have to be sealed on the backside prior to filling. There is also a fair amount of bark in some of the holes, which I would like to retain to add interest to the finished table. Any suggestions as to the optimal product to use as a fill material, and/or techniques that would maximize the opportunities for success on this effort?