The tricky bits - I started each scrap by gluing down the inner edge where the glass will press against the frame, then I spread the rest with glue and smoothed it down. Also, I cut mitered corners in order to get a fairly neat look at each corner. Then, I trimmed all the excess fabric from the back edge of the frame.
After an hour and some brand new blisters, the first frame was ready to go. The base is a cheap IKEA frame, simply because my trip to the thrift store was fruitless.