Print out the free pattern. Once you've printed it out, cut the three pieces out and tape them together after matching the lines and letters along the edges. Start by pinning the pattern on the flannel (folded so pinning through two layers) and cut out around the outer edge. Also cut out one of the Cotton Batting (or fleece iron on interfacing). Place the two pieces of flannel right sides together with the batting underneath. Pin all three together around the outside edge of the fabric.
Sew a straight stitch ⅜ inch from the edge all the way around the edge of the burp cloth, leaving an open edge that's about 3 inches wide. Backstitch at both the beginning and end of the seam.
Clip little triangle wedges out of the seam around the rounded raw edges of the burp rag, being very careful not to cut into the seam.
Turn the burp rag inside out (right side out) through the opening you left on the edge.
Press out flat and turn the edges of the opening to the inside along the seam line. Pin the opening closed.
Stitch close to the edge all the way around the burp cloth and over the opening so it is stitched shut.
I went ahead and sewed straight lines across the burp cloth about every two inches to keep the cotton batting from bunching up when washed. You could make a cute criss-cross pattern, or use decorative stitches if you want. It's kind of "quilting" it together.
Now make a few more to create a giftable set!