I can't say much about the winging it as that is what I generally do, I have done some quilts just from pictures,
Take a few to practice on, cut the batting and the backing square out, and your strips for the block, place the center square in the center and tack it down, place your first strip on , right sides together and sew, I would finger press out especially if you are using poly batting, it will melt if you iron it, then continue in this way,
Do you have measurements for the block?