Here’s how I do a running marker. First, take some wast yarn in a contrasting colour that is a lighter weight than the main yarn. I use about three times the length of the finished piece. Obviously it helps to have an idea of how big your piece will be but a rough guess is fine.
I usually work the first two rounds before placing my marker ready for the third round.
You place your waste yarn just after the last stitch worked. You can see here why you need a lighter yarn. If it is too thick, you can’t see your next stitch to work and it distorts the shape of your work.
Then you work the next round as normal. When you finish the last stitch and are ready for the first stitch of the next round, drape your waste yarn back to the front and work the next round.
When you get to the end of the next round, drape it back and continue. Easy as that. It will start to look something like this.
And by the time you’re finished your piece will have a running marker and you will be able to see where your start of round is. And if it’s drifting.