I've been thinking about starting this project for quite some time now and finally went to the Home Depot tonight to get some supplies.
To make the cutting process easier, I decided to use option 2, without the interlocking corners:
The cuts turned out more nicely than I expected them to. That made me happy.
Tomorrow, I'll drill some holes in the frame and get it all put together. Maybe I'll find some time to visit the fabric store. I have an idea for a painting that would look really neat on a printed fabric canvas. I hope it turns out as nicely as I imagine it will.