You will find a collection of drills in here sorted alphabetically that are best done with fins. If you are a competent swimmer you can certainly try these without fins. Perhaps just do 10 or 15 seconds worth and then swim.
If you aren't a competent swimmer these drills will be difficult to do without fins. We suggest you swap for a drill without fins or swim thinking about a certain part of your stroke.
What FINS Should I have - there is a video on that inside the collection