Yes, I was lazy so it was quick and dirty. I washed it, sliced it raw and laid the slices on a wax covered cookie sheet. When frozen, I packaged the pieces in baggies. By freezing individually, I can use only the needed amount. It worked well as long as it was used in soups, stews or other cooked dishes. Never tried it thawed and raw.
I tried both drying and freezing celery, using small slices. The dried celery lost so much moisture it seemed to disappear; have not tried to cook with it yet (too scared). I also dried slices of carrots. I really need to try to cook with them - I spent enough time preparing them.
I froze celery 2 ways (blanched and not blanched) and cannot tell the difference after cooking: I like to put about 1/2 cup in stews or soups. Frozen tastes fine. I used small baggies for the freezer.
I have also been separately freezing sliced sweet peppers and sliced sweet onions: works great for fajitas.
Lazy here too. The store had two for $1.00 on the long stalks, so I grabbed two. I washed, sliced what I thought was good for soups, and layered those amounts in between wax paper in a storage bowl. I have one left to deal with and better get to it before I forget it's in the crisper.
I sautee celery and onion, twice as much as for a recipe..and freeze half. Green peppers, I toss them in the freezer whole...they are fine for cooked dishes...like chili and spaghetti...although I have used thawed and diced green peppers in my crab salad. It tasted fine.