For a 2x4 fleece liner you would need 68” of fabric, which is 4” shy of 2 full yards. If I were you I’d get the 2 full yards just to allow for shrinkage when you do your pre-washing.
If you want to make a fleece pad for the whole cage you probably would want 4 yards, 2 for the top of the pad and 2 for the bottom.
You asked how to clean a C&C cage…does this mean if you’re using fleece? If so, then you just sweep or vacuum up the pops once or twice a day and change out the fleece once a week.
If you have at least 2 sets you can put a new one in as soon as you take the old one out. If you only have 1 set of fleece then you can take your pig(s) out for floor time while the fleece is being washed and dried.
Additional – When you take your fleece out to wash you want to sanitize your coroplast base. Use a 50/50 water and white vinegar solution and scrub the inside.