The best "design" for manual laundry is two buckets, 5 or 10 gallon, and a clean plunger. First bucket is wash, second bucket is rinse. There are manual wringers that help duplicate the spin cycle of a washer, but if I was washing a lot of cotton clothes, I wouldn't bother. They'll take 2-3 days to dry, and will smell moldy unless you do it outside in direct sunshine.
If you're washing synthetics, it will work great even for indoor drying. That's why a lot of dedicated backpackers and road warriors wear all synthetic underwear, for instance. Easy to wash and dry even in a hotel.