Trim the artichokes: Cut the bottoms off the artichokes so they sit flat.
Cut the very tops off the artichokes (see notes)
Add the artichokes to the slow cooker.
Sprinkle over with salt and pepper, then add the garlic.
Squeeze over the lemon juice.
Cut the butter into slices and place on top of the artichokes.
Add the water to the bottom of the slow cooker.
Cover and cook on HIGH for 3.5 hours without opening the lid during the cooking time.
Serve with melted butter (or mayonnaise if that's your thing).
Video
Notes
See my photos for cutting the tops; I did about a half inch. If you have a hard time getting the artichokes to fit, peel off a few off the leaves and that should allow them all to fit nicely.