How to finish a round with a slip stitch in a crochet chart
A slip stitch closes the round. Place it, select it and press Finish round.
Steps
Work your round until the last stitch is placed.
Choose Slip stitch in the panel and place it right after the last stitch, between that stitch and the standing chain. Rounds are worked counterclockwise. With the standing chain at 12 o'clock and the last stitch at 1 o'clock, the slip stitch goes between them.
Choose the Select tool (or press V on the keyboard) and click the slip stitch.
On the small toolbar, press Finish round. The round is closed.
Try it here
Good to know
Why not on top of the chain?
A pattern may say "slip stitch into the top of the beginning chain 3". In a crochet chart, though, the joining slip stitch is drawn after the last stitch of the round, not on top of the standing chain.
Stitches that do not clearly belong
If some stitches do not clearly belong to the round you are closing, Chain One asks which ones to count, so your stitch counts stay right.