Thanks to Angi for this Frugal Baby Tip!
Lay the prefold in the cover, thick panel running from back to front, roll the edges in towards the centre until it's the right width. You then have "barriers" at either side, but they are not too big & uncomfy and really liquid poop will ooze into the roll or stay in the middle.
Put wrap/prefold under baby bring front up between legs and fold over any
excess, close wrap.
Hope that all makes sense. Works good for runny tummies too!!
PS. If you tend to get blowouts out the back, you can make a little roll or
fold down at the back after rolling sides in - play around to get best fit
for you (or rather your baby)