OK... Start with this site...
http://www.bellaonline.com/articles/art10208.asp
Now take your finished square size. say 8 inches. divide by 2 = 4 inches.
Each four square in the pattern needs to be 4 inches square finished size. That makes each four square 4 1/2 inch. You need four of these, two of one color combination, two of the other. Take the 8 inch example here. You cut a block of one color 4 7/8 inches square. Cut the matching block color for that HST 4 7/8 inches. I personally would use 5 inches and trim later.
Place the two fabrics good side face to face. Pin so all four edges are even with each other. On the lighter fabric, draw a line from corner to corner. Now draw two more line a scant 1/4 inch from the center line one on each side of the center line. Sew right on top of those 2 lines. Leave the center line un-sewn. Cut the blocks down the middle of the block along that line that goes corner to corner. press open the two HSTs and you have half the 8 inch block done. Do the same with the other two fabrics. Trim all blocks to exactly 4 1/2 inch and square.
You now have four squares 4 1/2 inch square. Using the photos shown in those pictures, line up the left side and sew together, line up the right side and sew together. Now sew the two halves together.
Done. I don't know what you would do with a pattern.
tim in san jose