Tonight, I began the tedious process of fine tuning the joints in the frame. I only had about 45 minutes to an hour to work, so I was only able to work on 5 joints. Here's a photo of how they are turning out now that I'm extending the slots by approximately 3/8".
Now, I'm much more pleased with the joints. I'll keep working on all of them until they're all smooth. Then, it will be time to start pre-drilling screw holes and planning out the gluing and clamping process.