I use soap sacks. They're little woven bags about the size of a bar of soap. All my slivers go in there and that's what I use in the shower.I just take the almost empty bottle out until there is enough space in the full one to upend the almost empty one over the almost full one and let it drain for the day. It usually needs to be propped so the kitchen is more convenient than the bathroom - there are more containers to use for propping.
Does anyone have a good method for using the slivers of bar soap that are too small for certain people (like dh) to bother with? For a while, he would "glue" them onto the new bar by pressing them while both were wet. That used to work pretty well, it would be a fragile bond for a few days, then be strong enough to hold well enough. Lately neither of us can get them to stick hardly at all.