This sophisticated cousin of the half-square triangle unit can be used in any half-square triangle block you can think of, and is made quite simply. Starting with a half-square triangle unit, you add a smaller square and sew along the diagonal using a stitch-and-flip technique, much like you use in improvisational piecing.
For one Double Flip HST unit, you'll need:
5" print square
5" solid neutral square
4" print square
1. Begin by using a clear quilting ruler and tracing a line across two corners of the neutral 5" square, marking the diagonal of the square. Use whatever type of marking tool you prefer.
2. Align the raw edges of your neutral square with a print 5" square, right sides together. Stitch a scant 1/4" on both sides of the diagonal line you traced, then cut along the traced line to separate into two units. Press seams open and trim HST unit to 4 1/2".
3. Using a clear quilting ruler, trace a line across two corners of the 4" print square, marking the diagonal again as you did in Step 1.
4. Place this square at the top of your solid neutral half of the HST unit, making sure that the diagonal line you've traced is parallel to the HST seam in the center. Stitch along the diagonal line, and trim the seam allowance to 1/4". Press.
5. Ta da! A finished Double Flip HST unit.
NOTE: This type of unit can be constructed using any size half-square triangles. Just be sure to cut your accent print one inch smaller than your HST. This will create that skinny strip of solid neutral between your two prints.
For my Double Flip mini, I made a total of 16 of these blocks, and arranged them in a diamond formation.