Posting up weaker defenders? How many players did Malone post up who were stronger than he was?
I don't understand what you're asking. Are you implying Malone often posted up against stronger players? Malone was the strongest player of his generation. In later years, Shaq was bigger, and Robinson often gave Malone problems, but outside of those two, no one was as strong as he was.
By-the-way, saying he posted up people but couldn't create his own shot -- seems to be some incongruity in those statements.
Have you played basketball? When you post someone up, you simply put yourself in a position where you can receive the ball from someone else. That's was posting up is. That's what Karl Malone did. He posted you up, or he played a perfect pick and roll; both offensive strategies that require the help of another person.
You might be mistaking "posting up" with something Charles Barkley used to do a lot. He would receive the ball near the arc, and then slowly back his opponent down toward the basket, either shooting a passing from a double team. The difference between the two players was that Barkley could get the ball there by himself. Malone did not do that. He moved to a position without the ball and waited to receive it.