A sharp knife, a round file, a steady hand and some patience can get you a long way. This is probably not placement you're going to us, but the picture might work as inspiration:
This is the placement I chose. It's attached with this super glue. For this particular one, I had to remove the speaker and bend the connection pins on the jack, so it was a tight fit. 
Then I used a knife to make rough hole. I started out with a smaller v-shaped hole and worked my way down to vertical cuts. 
Here comes the cheat. I used a round file to even out the hole. If you don't have one, you just have to buy one. 
Also notice that I've removed some of the plastic normally holding the speaker in place.
Here's what it all looked like when assembled. For this particular method, you really need align everything correctly, since the glue dries instantly, and the hole can't be undone. In fact, I misaligned the Prosound jack on this one slightly by putting it too far into the GB, which means that most 3.5 mm plugs won't fit unless you press them in firmly, and they tend to fall out. This could've been avoided if I had just placed the jack 1 mm farther out before the glue dried. Lesson learned though.
. It took me months to write this tutorial because its so boring to fire on latex after your regular work, create the figures, etc.