The idea behind my attached i-cord corner method came, not surprisingly, from quilting. Most quilts have attached bindings whose corners are mitered. It was seeing this miter that inspired me to create a better attached i-cord corner.
The first way is to knit out from the project. Stitches are picked up around the project, ending with a very large number of stitches. These are joined in a circle. Then one row of edging is knit at a time, so the width of the edging is easily adjusted. Increases are made in the corners.
The first type of knit-out corner involves having a corner stitch or two (or even three). Increases are made immediately before and after this corner stitch, resulting in a very obvious miter.
The second type of knit-out corner does not have the corner stitch. Instead, an increase is made after the last stitch of one side, then another increase is made before the first stitch of the next side. The resulting miter is not so visible.
The second way to knit an edging is to knit around the project, one stitch at a time. Stitches around the project are added to the edging every other row. When the starting and ending stitches meet, the edging is grafted. The number of stitches in the pattern is set before knitting the edging. The edging may involve a lace or cable pattern with increases and decreases, but usually the number of stitches one starts and ends with remains the same.
The first type of knit-around corner applies to flat edging. The edging is knit back and forth in right- and wrong-side rows.
1: It's attached to the project by knitting together the last stitch of edging with a stitch on the project. Knit to the last stitch of the project before the corner stitch.
2: Short rows, knitting one less stitch every right-side row, create a diagonal. When there are only 1 or 2 stitches left, knit the "miter" row.
3: On this miter row, all wrapped stitches are knit, and the last stitch is knit together with the corner stitch on the project.
4: The short rows are reversed, where knitting starts with only 1 or 2 stitches, increasing every right side row until all edging stitches have been knit.
5: Once all edging stitches have been knit, return to knitting flat edging.
The second type of knit around corner applies to i-cord. The edging is knit in rounds.
1: I-cord edging is attached the same way as flat edging. Knit to the last stitch of the project before the corner stitch.
2: Continue with i-cord rounds, knitting one less stitch per round until only 1 or 2 stitches are left. Knit the "miter" round.
3: On this miter round, all stitches are knit, and the last stitch is knit together with the corner stitch on the project.
4: I-cord starts with only 1 or 2 stitches, knitting 1 more stitch per round until all i-cord stitches have been knit.
5: Once all i-cord stitches have been knit, return to knitting regular i-cord edging.