Home enemas from mom were in the bathroom. At first I was in the tub on my back, feet up on the wall on either side of the spigot (age 10). Once she was convinced I wouldn't ‘make a mess’ she had me lie in the same position on a bathmat on the floor (feet on the tub side). That switched again over time to me on all-fours, knees-elbows and/or knee-chest.
My cousin got his enemas in bed. The same bed I shared with him when I stayed there. And when I stayed there we both got enemas on that bed. While my aunt prepared things, we got naked and spread several towels across the middle of the bed. We'd decide who went first and that person then got in the Sims position with their butt over the edge of the bed, the other on the bed nearby.
My aunt used a standard 2 quart bag which we shared, she would arrive with the full enema bag, a jar of Vaseline and a hand towel. She'd might adjust our position and then get a generous dollop of Vaseline on her finger. She'd lift a cheek, maybe make a comment about our cleanliness and then slide her finger up our butt, rotating back and forth once or twice. She'd wipe her finger on the towel and then insert the nozzle and release the clamp. When she thought about half the bag had gone in, she would close the clamp and remove the nozzle. That boy would then slide out of the way and the second boy got into position. The same routine was repeated on the other boy. I thought it a little strange that we would ‘share’ the same bag, water and nozzle, but I had only had ‘solo’ enemas before. Both enemas were delivered in what seemed like a minute or two each.
My aunt valued retention time over volume, so there was to be no mad dash to the toilet when the nozzle came out. We'd roll or slide out of the the way and would wait while the other got their enema. It was a relaxing atmosphere, the room was dimly lit with us lying side by side watching and listening while one was getting their enema and the other was either was retaining their enema or waiting for their turn. With the bag empty we were still expected to lie quietly holding as long as possible. My aunt stayed with us to enforce the quiet waiting time and releasing us to the bathroom when she thought we had retained long enough. We'd mostly lied there quietly, but might get the giggles when one of our guts grumbled. Also with two boys involved, everything became a contest. We'd each try to outlast the other regardless of who may have gone first.