Here is the third square in my Nightmare Before Christmas Afghan.
This square is knit instead of crochet. However, if you don’t knit. You could follow the chart and do it in single crochet.
Here are the links to the other 2 corner-to-corner (C2C) patterns:
Enjoy! Please share your projects so I can add photos to my Ravelry page.
Tricia's Ball of Yarn & Scott Family 
On the ones that are knitted, if I were to do it in crochet as you suggested, would it be a c2c as well or just a standard sc going across as you go? I’m new to this stuff but want to save this for future trials.
I would do sc across. Corner to corner would make it much bigger.