2) Thread hole first
Drill a hole through both cortices, using the drill for the thread hole.
Then use the corresponding larger drill bit to overdrill the near cortex to
create the gliding hole.
This technique is useful for small fragments. The disadvantage, however, is
that the holes may not be centered in relation to each other.
If the near cortex is tapped prior to overdrilling for the gliding hole,
eccentric passage of the second drill is less likely. This can be achieved by
inserting the chosen self-tapping screw through the near (cis) cortex and then
removing it. The drill will now follow exactly the threaded axis.