I never used a slow cooking crock pot. Always used a 6 quart pot on top of the range.
The longer you cook your stew, the thicker it will get. I cook my stew for 3 hours. But cook it that long, and your veggies will get mushy or will disintegrate. That can be cured by adding some of the veggies later rather than sooner. I prefer bigger chunks of beef, which get nice and soft the longer you cook the stew.
I like to use Angus beef, and large cuts of potatoes, carrots, onions, sweet pepper and celery. If I have green beans, I'll throw those in too. I use water as a base. First I brown the beef, remove it from the pot, then caramelize the onions in olive oil. Then re-add the beef, add 3 cups of water and add the other ingredients on a schedule.
What I like to do to add flavor, is to substitute 12 oz of water with 12 oz of a good ale. Something like an Irish ale or brown ale, but not an IPA. Also Worcestershire sauce is a good additive. I will also throw in some salt, thyme and tarragon. A 4th cup of water goes in after 2 hours. For a thickener corn starch is recommended.