Well obviously, I'm using flats as diapers. My fold of choice is a basic rectangle fold.
I start by laying my flat on the floor.
Then I fold it into thirds. If It's a narrower receiving blanket, then I will just fold it in half.
For the Spain's size*, the diaper needs to be about half the length. I fold one end over. This will be the front of my diaper.
I fold the flap over one more time. My diaper is now a good size for Spain.
To put this diaper on Spain, I bring the front corners together. This will make a nice leg gusset to contain any nastiness that might try to escape.
Time to add a little baby.
Then I pin the diaper one side at a time.
And we're done!
*I figured this out through trial and error. I fold the diaper, stick Spain on it and then see if I need to make it shorter or longer.