Several sellers shared some suitable fonts (Thanks, guys!), then Molly, over at Lessons by Molly, told me how to make my own!
Here is how to make open letters:
1. Highlight the letters you want to be open.
2. Under “Format”, click “Text Outline”. You can adjust the weight of this line as needed.
3. Under “Home”, change the font color to white.
Here's what your letters will look like:
Have fun making your own beautiful letters!