For this you will need:
1 flat cloth diaper - they still sell these in big box stores but I prefer to use old flannel sheets, you could also use a flour sack towel.
Diaper cover (optional)
Fastener - snappy, pin or elastic belt (optional)
Spread your diaper on your surface/changing table.
My diaper is much smaller than standard size.
Gather together the bottom corners and lift.
This will create a triangle with an extra flap.
Lay the flap to one side.
Fold 1/3 or 1/4 of the flap toward center (depending on the size of your diaper).
Fold in again
Optionally, you can fold the corners of the triangle up for a trimmer fit around the legs.
Place the baby on the folded diaper.
Bring the triangle's corners to the front. Here you can tie, pin, snappy or secure with an elastic belt.
I like to tie. I usually knot it and the front can be pulled from under the knot if you're practicing Elimination Communication and baby needs to use the toilet.
If you desire waterproofing, a cover would go on at this point.