I've had many many requests to make this how-to available.
This is not an original idea, nor do I claim it to be. There are a trillion patterns for mitred square blanket, therefore I am not claiming this as an original pattern, but rather a how-to.
This is the version that I posted on my blog earlier this year as to how I am knitting my mitred square blanket; seamless and modularly, knitting each square onto those already complete. I'm sure this is not original either.
I've knit my squares in DK weight yarn but this how-to is easy to adapt to other yarn weights, for example, if you wanted to yield a similar size square but knit in sock weight yarn, cast on 26 stitches and aim for a tension of around 28 stitches over 4". Worsted weight at 20 stitches, cast on 18.
The sample was knit in a variety of yarns, including WOOLganics Organic Merino 8ply/DK. A substitute yarn is shown below.