The simplest way to knit Fair Isle or stranded knitting projects is to work them in the round, even if the finished project is intended to be flat or have slits such as arm holes or a cardigan opening. It's much easier and faster to do stranded knitting all from the right side (and harder to get lost in your pattern).
The only potential problem with knitting a project that's supposed to be flat or have openings in the round is that you have to cut your knitting to make it the right shape. That's accomplished by knitting and cutting a steek, which sounds incredibly scary, but once you've done it once, like so many other things in knitting, you'll wonder what the fuss was about.
To knit a Fair Isle or stranded knitting project in the round that's meant to be flat, you'll have to add a few stitches to make the area where you'll cut. Patterns can have as few as 4 or as many as 10 steek stitches.
In my Steek Sample Swatch, which is shown in this tutorial, I used four steek stitches. They were worked by simply alternating colors across the stitches, and they're easy to see because they break up the main pattern of the project.