Lets say the heel flap is 36 stitches across, then knit the heel as follows:
Row 1: k23, ssk, turn
Row 2: sl1, p10 p2tog, turn
Row 3: sl1 k10, ssk, turn
Row 4: sl1, p12, p2tog, turn
Repeat rows 3 & 4 until all stitches are worked. Now knit across heel stitches and pick up the appropriate number of stitches along the side of the heel flap. Knit across the instep, in pattern and pick up the appropriate number of stitches on the other side of the heel flap. A few decreases may be needed along the gusset to return you to the correct number of stitches, in the case of this example, 36 stitches.
The finished heel:
How does this heel compare to a traditional heel flap with gusset? The heel created is narrower than the traditional heel flap / gusset combination. The Dutch heel seems to wrap the heel nice and snug. The decrease stitches are at the bottom of the Dutch heel while they are at the back of the heel, where heel flap and sole join, in the traditional heel flap / gusset heel. The dutch heel doesn't have much of a gusset, while the heel flap sock has a gusset. I didn't feel the decrease stitches when walking in the sock, but I can imagine this won't be true for everyone since the heel flap and hence the decrease stitches wrap under the heel. I can also imagine that on a less stretchy pattern, it may be hard to get a sock with this heel on your foot. Guess I need to do more dutch heels.
Photos copyright Prairie Willow Knits; Twirl pattern copyright numma numma llc