I used a 1.25" x 1.25" x 5.25" piece of wood I purchased from a friend. I shaped and rounded 3 corners using a Sawrasp leaving 1 slightly square. Next I put her to the Belt sander and finished with 320-2500 grit sand papers. I drilled the tang hole using a 1/8" bit on my drillpress. Shaped the tang using a Dremel grinder attachment (gave the choil and spine some love while I was at it) and stuck it in place using small wood wedges and 2 Ton Epoxy. Finished with Mineral Oil.
Marko's handles are amazing! I think I will attempt tapering with the next D-handle I make. I am also looking into stainless or copper bolsters for the next one. I love that look with single wood piece handles and possibly a mosaic pin or two.
But for the first attempt I wanted to keep it simple.