You can encourage them to go in a certain spot by keeping their hay, food dishes and water bottles in the same area. They poop the most after eating so it will be more contained in that area. I use hay bins in my cages and one guinea pigs insisted on jumping in there to do her business. I removed the bin and put the hay on a smaller piece of fleece in that corner. The majority of poop is there now. I don't care for "kitchens" because it's another section to maintain so the fleece piece works well for me. I just shake it out and replace daily and wash it with my other fleece.