OK, I have a small cheap crockpot. I want to make cannabis oil (only because it keeps longer and doesn't need to be fridgerated). What exactly do I have to do to make cannabis oil? I don't want to waste an ounce of weed (no access to trimmings, shwag, shake, etc.)

What heat setting?
How long?
More time = more potency?
Which is the best oil to use? Coconut? Canola?