Round 1: knit the stitches on needle one until the last three stitches, knit the next 2 together, then knit one. This will end needle one. Knit the stitches on needle two. On needle three knit one stitch, the with the next two stitches SSK, slip the next two stitches then knit them together like we did with the heel, (or you can slip one stitch, knit one stitch and then take the slipped stitch and move it up and over the knit stitch off the end of the needle). Continue to knit the remaining stitches to the end of needle three. With this round we decreased by two stitches total.
Round 2: knit
Repeat round 1 and 2 until you have the same number of stitches as you started the sock. With these socks it is 56 stitches, so now I have 14 stitches on needle one, 28 on needle two, and 14 on needle three.
Once you are at this point the gusset is completed and we will be knitting the foot of the sock. To do this you just knit, in rounds, even (no increase....no decrease) until the sock measures 2 inches smaller than your foot (measuring from back of heel to end of longest toe).