Paul equates his teaching of faith and salvation in Jesus Christ to laying a foundation for a building. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Paul is referring to the person or people who are teaching the Corinthians at that time as if they are carpenters who are constructing the building above the foundation. (See: [[rc://en/ta/man/translate/figs-metaphor]])
This can be stated as active. AT: "no one can lay a foundation other than the foundation that I, Paul, have laid" or "I have already laid the only foundation that anyone can lay" (See: [[rc://en/ta/man/translate/figs-activepassive]])