Did a Celtic Heart Quilt. The instructor had us cut strips big enough to turn out as 3/8" and extra for sewing seam.
Just sewed a 1/4" seam on the bias strip, wrong sides together, trimmed the strip and pressed the seam to the bottom using a presser bar. She said no one would see the seam anyway. We cut strips in various lengths, and always joined the strips when they went UNDER another strip. Then you didn't see the join.
I've forgotten the size of the strips, but just did a stained glass wall hanging and didn't feel like using the premade strips. These strips were a tad larger, but they worked.