I like a wider binding and usually use 3 plus " you keep the same seam allowance and when you get to the corners you do them the same way but make sure you have the correct measurement to turn your corner. I usually have to fold my fabric at about 3/4" -1" depending on how large my binding is going to be. just make sure to measure everything as you go. Also I always trim my top once the binding is on the front then iron and fold to the back to sew it down.