Oh the mitered square is easy! After you know how many sts to cast
on for the size of block you want, for a mitered square you will cast
on double that. So in the example above it was 54 sts for a 12" square so to make a mitered square I would cast on 108. Then, what I find easiest when doing them, place a marker at the halfway
Row 1: Knit all the way across.
Row 2: Knit to two sts before marker, ssk, slip marker, knit 2 together, knit remaining sts.
Repeat rows 1 and 2 until there are 4 stitches left and you are
ready to do another decrease row (row 2). SSK, k2tog-2 stitches
left. Next row K2tog and finish off (pull yarn tail through remaining
stitch to finish).
When you start the cast on edge is flat like ____, after knitting for a bit and doing the decreases the cast on edge will start to look like
this \__ and when you are done the cast on edge will be like this
Google Mitered squares in knitting or domino knitting and you
will find tons of info on it!
This is a great square to get practice using the left leaning ssk and
right leaning k2tog decreases