I am just in the process of sandwiching Blueberry Buckle from Jo Morton's book and it is done in flannel, with the exception of the centre square. When working with flannel, I always prewash because that stuff can shrink like crazy. I then take the time to square up the fabric and just go from there. I always pin even when my seams are nested. I'm always concerned that they will shift when sewing them. For really tricky ones, I glue baste it using a washable glue stick. If I have enough fabric, I increase my seam allowance to almost 1/2" since I find that flannel tends to fray a little more than some other fabric. I am not a fan of dense quilting, especially for quilts meant for warmth - I like to be able to "cocoon". My backing is also flannel and so I do have that super-soft feel. Good luck with the quilt. Please post a picture when it is finished. I, and I'm sure everyone else, would love to see it.