Assuming you stay with the orientation above, draw a guide line on the right side (in line with your left stitching line), push the awl through from the left side you have punched, take it slow and see where the point of the awl is just starting to poke through, if not on your guide line, pull back a fraction and adjust your angle to come through right on your line. You don't have to punch so deep that it deforms the leather. Your awl will take you through all the way. Awl needs to be really sharp. You might need a flat jaw pliers to assist pulling the needles through. (No grips in the pliers jaw so you don't wreck the needles.)
Either Dwight or Ferg have posted instructions for the way they do stitching in thick leather. Do a search for their posts.