This video shows you 5 different ways of joining granny squares so now you have choices! The different ways of joining the squares will create different effects. If you just sew them then that can deteriorate over time especially on a big blanket and you might find yourself resewing the squares together down the track. Bags need stronger seams on the granny squares too. When you are at the stage of sewing the squares together then think about he yarn you are using and the purpose of what you are creating. If you join the squares as you go it means you cannot change them and sometimes you want to . I enjoying having a pile of squares and working out different ways of putting them together so I don't attach them as I go. It depends on you and it depends on the sort of granny squares you are making.In any case, knowing different ways of putting the granny squares together helps you to choose the best way for your project.