Here's how to saw slots in the middle of something without drilling holes first.
It's called a "plunge cut". This particular method works with a sawzall, sabersaw, handheld jigsaw, or whatever you want to call it.
You've all learned the drill-holes-for-sawblade technique already in industrial Arts class.
For this plungecut method, you don't drill any holes.
You just start the saw, rest it on its guard, rock it forward, and BELIEVE!
If your faith is pure and you do it just fast enough the blade doesn't stub its toe and get bent.
In these pix Fungusamungus
and myself are cutting slots for a skeg box on a CLC boats "Pax 20" kayak.