Those look like Torx three piece fasteners. They have stepped or straight barrels that go inside the hole in the tang and then screws are applied from each side. You, of course, would not grind these flat to the contour of the handle but would leave the handle flat with no more than rounded off edges. You would also need the appropriate size Torx head wrenches to attach them. Jantz sells a full set of wrenches for about $5 or an individual wrench for the same price. I imagine that you have that problem figured out already. Seriously, I got a full set at a knife show for about that amount.
Jantz's catalog has step drill bits for them and instructions on how they are used. Tracy at USA Knife Makers Supply may also list instructions on his on-line catalog.
Doug