We use hampers that sit in the bathtub. When full they are emptied into bags or pillow cases and stored in the back of the truck. When we use the tub they sit in the bunkroom.
We have an undersink storage but it would only be large enough if we only went camping for two or three days. We used it for white clothes at first but then we decided we would not take any white clothes and use it for extra toilet paper and boxes of Kleenex.
We take enough clothes for 12-14 days so we need alot of space for dirty clothes. We are often 40 miles from a laundromat.