I don't yet have a bishop bag for my DD tarps, but the 3x3 I fold neatly on the ridgeline, then wrap the ridgeline around it to slightly compress the entire thing and hold it all closed. This then just goes directly into the rucksack.
Similarly with the DD XL (4.5x3), though sometimes (depending on the rucksack I'm carrying) I strap it to the outside merely because it takes more room.
With the DD 4x4, I have made a snakeskin, and the whole thing gets bundled into a PLCE Bergen side pouch.
I don't waste my time with the bags the tarps come in... it's just one more thing to have to fiddle around with that, if you've set your tarp up properly to begin with, isn't necessary.