The workers who did this at Jeroboam's commands are represented by the metonym of the name of Jeroboam himself. Alternate translation: "Jeroboam's workers made houses on high places" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The implied information is that these were houses of worship. The full meaning of this statement can be made explicit. Alternate translation: "houses of worship on high places" (See: [[rc://en/ta/man/translate/figs-explicit]])