I cooked 3.5 pounds of corned beef in the crock pot last week with the intentions of making reubens. Taste wise the dish was great, but the corned beef fell apart and I did not get those pretty deli slices I was hoping for. I cooked the beef according to my butcher's recommendation, and verified the cooking time later with an online resource and they were pretty close. Did I miss something in the process or is there a better preparation method other than a crock pot for cooking corned beef?
Did you let the meat cool completely before attempting to slice it? Even meat that is completely-fall-apart tender straight out of the (crock)pot will firm up quite a bit when cooled.
Your corned beef fell apart because you used the crockpot, typically things cooked in there fall apart very easily. This is great for tender meat, not so great for sandwich making.
Cooking your meat in a stew pot would definitely have better results. It may be possible to cook the meat on high in the slow cooker to get a better result.
You could try wrapping it in Caul or something similar, which will help keep it in once piece.
Corned Beef only needs to be brought to a simmer from cold water for 35 minutes per pound and then turned off and let cool in the liquid this will give the best results by cooling in the liquid you will have moist flavorsome corned beef