Knitting

 Small squares

Cast on 45 stitches in contrast yarn

Knit one row,

Next row knit 20 stitches, k2 together tbl, knit 1, k2 together knit to end

3rd row knit 21sts Purl 1 Knit 21 sts  

Change to contrast colour and continue to decrease as established until 3 stiches, knit one row, knit 3 together.

4th row, knit 19 stitches, k2 together tbl, knit 1, k2 together knit to end

I made up a graph as I wanted to create diagonals colourwise. I also used the main diagonal colour in the other corners too.

when you are placing the squares you will note that 2 edges do not have the contrast colour - I usually pick up the stitches along the edge knit 3 rows and then cast off. 

here is a link to a mitred square blanket which is a no sew - https://www.purlsoho.com/create/2019/01/09/mitered-corner-blanket/