I think this recipe came with my new Crock Pot when I got married in 1976. I served it for the first fancy meal we had, inviting our pastor and his wife for dinner. It got rave reviews. I hope I have remembered it correctly.
Sear roast on all sides by placing in a very hot greased iron skillet and turning every couple of minutes.
Place roast in crock pot on low. Pour the water around the roast. Sprinkle with pepper and a little salt if desired. Place the garlic and onions over top of the roast. Cover crock pot and cook on low 6 hours.
With a meat thermometer, check the thickest part of the roast for doneness. I cook until it reaches 160 degrees. When done, remove roast from crock pot with 2 large spatulas or spoons and place on serving platter.
Take meat juices and onions from crock pot and place in sauce pan. Dissolve 1/4 cup flour in 1/2 cup water and add to drippings. Boil as for gravy until thick. Add more water if necessary to achieve desired consistency.
This roast should slice - it does for me. The cooking time is approximate depending on the size of your roast and how the crock pot cooks. I used the medium size crock pot - about 3 quarts capacity.