Trying to combine 3 of 4 cells in a square in a table in word

Question

I am trying to merge specific cells in a table. The table is setup like this:

1    2

3    4

I am trying to merge cells 3, 4, and 2. However, it will not allow me to do that. If I wanted to combine 3, 4, and 2, I would need to include 1 as well. Is there a way to do this and create this reverse-L shape?

Thanks!