Check your measurements very carefully. Each block should measure 12 1/2 inches when it is finished. Accuracy from beginning to end will assure that your blocks come out perfectly. Measure carefully, sew carefully, and you will have a perfect block.
For the Oh Susannah you will need:
From your background, cut four 3 1/2 inch squares, and cut one 3 1/2 X 15 inch strip.
From your color 1, cut one 3 1/2 X 15 inch strip
From your color 2, cut four 3 1/2 X 6 1/2 inch rectangles.
Sew your color 1 and background strip together, cut into four 3 1/2 inch sets.
To make your sewing easier, draw a line diagonally through the center of the wrong side of your background squares. This will be your sewing line.
Place a square of the background on the end of the color 2 strip. Sew diagonally from corner to corner. Trim 1/4 inch from the sewing line. Press seam allowance toward color 2 and away from the background.
Sew together four sets like this. These units should measure 6 1/2 inches.
Then arrange them to look like this, and sew together. Your finished block should be 12 1/2 inches.