Here's a sample setup without Trezor. Learn your 12 words by heart. Boot a diskless machine from a Tails CD (not USB). Tails has Electrum out of the box but you have to enter your 12 words every time you boot. Power off the machine if anything moves around your door.

This does not have quite the security of Trezor though. Check out Glacier Protocol for ways to crank up paranoia.