You can also:
1. SPLIT where you want the freeze,
2. Move the right part to where you want the freeze to end.
3. Then move back a frame and SPLIT again to single out a frame,
4. Then right-click on the single frame and click CREATE SUBCLIP.
5. Finally, grab the right edge of the single frame and stretch for the duration of the freeze.
I just did a project with a lot of freezes, and this was fast and simple (just three keystrokes, a slide, a right-click, and another slide), and easy to edit afterwards.