The phrase "lay upon" means to place or put something on top of something else. There are several synonyms that can be used instead of "lay upon," such as "place," "set," "position," "deposit," "rest," "park," and "plant." Each of these words can be used in slightly different contexts depending on the intended meaning, but they all convey the same basic idea of putting something on top of something else. It's important to choose the right synonym for the specific situation, but having a range of options allows for greater variety in writing and communication.