Same way. Stick it in and twist to make a perfect circle. Use like a nail for the carb.
Stick the knife in the side and in the top. Try not to go too deep from the top. The place the stem comes from can be used as the bowl, you just gotta get the knife to meet up with the sideways knife hole (or use a nail for this part too).
I've even seen someone make one with a lemon, a knife, then sticking a paper clip in the right spot.