How do I put Plants on top of items?

Plants can be placed on top of some items! As I've found that some people don't know this, I thought I'd post a thread!

The trick is you have to hold the plant over the floor square that the item that you want to place it on is on, as opposed to holding it as if you were going to place it on top of the item!

Here are some pictures to illustrate:

Holding the plant on top of the block does not work:

Holding the plant on the floor square that the block is on does work:

Alternatively, you can stack other items like speakers or trophies. Here's how you do it.