I’ve done the exact same thing as GaryM. The problem with bottom round is that no matter what you do it doesn’t have much flavor compared to all the other cuts. The best I’ve been able to do is to cook them at 61C (~142F) for 72 hours and then either make a gravy from the liquid left in the bag or slice it thin for sandwiches.
For bottom round cuts the thickness doesn’t matter much since you cook them so long anyway.