Edit: Thanks to napoearth
for pointing out this method is easier than I'm making it appear. In the below example all that's needed is to put the D on the 2x tile.
What this means is you need to use a 2x letter, 2x word, 3x letter or 3x word twice in one snap. It's not always possible, but when you see two of the same bonus tile try and see if you can make a snap that includes both bonus tiles. In order for it to be one snap the green outline must encompass the entirety of your snap.
Below is an example where I obtained this achievement. You'll notice there are two 2X letter bonus tiles, once I moved the P and D letters to these the achievement popped.