1. At the beginning of the row, add new color and knit one full round.
2. When you come back the first stitch you made in the new color, slip this stitch purl-wise. Knit one below in to the next stitch.
4. Cut the yarn with a tail to weave in later.
Optional: To add the next color, slip two stitches (the knit one below and the previously slipped stitch) and add new color into the first slipped stitch. This keeps the beginning of the rounds from “traveling”.
This technique is best for places in knitting where you want just one row of contrasting color separated by at least two or three rows of a second color.
For multiple rows of alternating color each round, helix knitting is a better solution.