After trying to figure out the best way to do this and with online research, I decided the best way to do it was to just make a piece of wood that would fit the cavity snug. The piece of wood I used was just a spare bit of 2x4 that me padre had laying around. I am gluing it in now and will drill the holes for the bridge, hopefully, tomorrow. So far, I spent about 2 hours getting the piece of wood to the right shape and gluing it in. My main problem was the piece of wood I used was a little twisted and I didn't pay attention to it until I would about 1.5 hours in. I tried my best to make it as snug fit as possible. It came out okay, definitely could have been better but I'm pretty sure it will hold.
Tomorrow, I will route the pickguard, assuming I can get the tele bridge installed successfully. Also, I don't have many wood working tools, so I am using pretty much all hand tools. With the exception of a drill press, which I'll use for the bridge installation.