Kneading dough by hand
Time and stretching will do the trick as well. Full on kneading or using a mixer is not necessarily required.  There are other techniques, such as "stretch and fold" or "slap and fold", which are generally used with high hydration dough.  Here is one example of a no-knead bread.  Also, This guy is a master...if I recall correctly, none of his recipes use a mixer or the kind of kneading that you are asking about.  It does take some practice to use the techniques he describes.  Bottom line:  using a mixer, or kneading by hand is not always necessary.