At a local flea market I got some old Norwegian yarn; it is 100% wool but of the itchy/stiff type. It is pretty hard to make garments out of it but very suitable for things that needs to robust and warm. So I made two flat pillows, intended for outdoor use to sit on when the weather is a bit cold. I used a simple “lifted stitches” technique where you knit back and forth (you purl on back side).
By knitting one colour first, the next two rows will be done by the second colour but you lift every fifth stitch. Then all stitches in the fourth row are knit with the first colour. I have used a simpler version on pillows before (see this post), and it is so easy to do and has a fascinating effect depending on how often you lift stitches and how frequently you change the colours. And as you can see, when using two colours, the colour you use when lifting the stitches makes the pattern look really different!
I prefer to have a woven textil as the back side as it makes it more sturdy. I just used some leftovers, it is actually a (quilted) bed spread (from IKEA) that I have used for similar projects before. I filled it with flat wool intended for quilting, it makes it just warm & soft enough to sit on!