Feeding the post is a two step process on the perimeter and a two step process on the block.
On the perimeter, your first job is to locate the target and create an angle. Basketball is really just 3D pool - there are all kinds of angles to get the ball where you want it to go, it’s just a matter of being able to create those angles and then execute them.
Unfortunately, the job of creating an angle is a lost art because most perimeter players see the game moving so fast that they cannot see the angles developing within the folds of the game. I love watching a veteran like Andre Miller create angles for post passes. He’s at a point in his career where he’s lost about three steps, and he wasn’t really all that quick to begin with, but it just makes what he does even more easy (and beautiful) to watch. You can see him surveying the defense and watch his thought process - I am going to stutter step, take one more dribble to my right with my right hand, fake like I am going to cross back over to the middle so I get my defender leaning, then throw the ball to my post man’s left shoulder. It’s almost like he is controlling all of the other players on the floor.
The second step once you have found your angle is to know what pass to deliver, which requires understanding how your post man has sealed his defender. There are entry passes and then there are scoring passes. An entry pass just gets the ball into the post. A scoring pass leads the recipient directly into their shot.
For instance, imagine a guy has his man sealed on the right block in a three quarter high spot (i.e. the defender is partially fronting the entry, with his right hand extended into the passing lane of the offensive players right shoulder). As a passer from the right wing you could a. throw a hook pass low and outside to the left hand, b. throw a chest pass to the outside left hand or c. fake the hook to change the defender’s balance and then flip the ball over the top. That’s three different entry options. All three get the ball into the post, but only one leads directly to a bucket, option c. If option c is delivered properly, the post man catches the ball turning directly to the basket which seals his defender behind him. If the ball is delivered on time and with the right amount of pace on it, the help defender won’t make it in time and the pass will lead directly to an easy layup or dunk. But most players can’t hit that pass. Instead, they just get the ball into the post, but without moving the defense to help the post man out.
But this isn’t all on the perimeter guys. The post man has two jobs as well. The first is to get a good seal and create a target. I remember when I was learning how to feed the post that our coach stressed that the post man must give the guard either a hand (to show where he wanted to catch) or a point (to show where he wanted the ball thrown on a lob). If I was given neither a hand nor a point, I didn’t have to throw the ball inside. Let’s just say our post guys made sure to give us targets because those of us on the perimeter were not shy about going somewhere else with the ball if there was no target. I see a lot of interior guys today that will seal but then not present a target, or present a poor target. The thing that made Jahlil Okafor and Karl Anthony Towns stand out last year was that both were very good at creating a seal and giving a target, which helped make them very good interior scorers.
The second job for a big man is actually catching the ball. Part of the reason many big men can’t give a good target is that they don’t have good hands. Many struggle to catch the ball away from their body. Because of this, it is difficult to feed them because if they are even partially fronted, there is no angle to get them the ball because they cannot catch with just their hands.
I have seen coaches working with big guys by throwing different sized balls to them in the post - tennis ball, volleyball, football, basketball - just to get them better at catching the ball away from their body.
Ultimately, Flip Saunders is right that small ball offers post up chances because having guys that can post smaller guys and draw multiple defenders is extremely valuable and will always have a place in the game.
