Welcome to the board from central Alabama.
Since flannel shrinks a lot, I would certainly wash it before doing anything with it. Clip the corner just a bit, quick wash in the sink, put into lingerie bag and toss in the dryer till almost dry, then iron to finish. Iron and starch well before cutting since flannel also tends to "creep" when you sew it.
Now for patterns. Since you are using a variety of patterns, I would suggest a simple pattern. Perhaps a charm quilt would work well. Here is a link to one. The blocks can be cut any size, but 4 or 5 inches works well for me for baby quilts. I usually use a decorative stitch over the seams for baby quilts since they will get lots of washing.
http://www.cozybabyquilts.com/quilt-gallery.htm