how to get dot 'n' dab boards behind the pipes?

[ColJack]

got to patch up a small bit of plaster behind the dishwasher, so I thought I'd give it a go myself as it's never going to be seen
I'll chop out the whole thing to the underside of the counter as it's about 1 1/2 inches thick one side and about 1/2 inch the other..

the problem is that the pipes run across about 12 inches from the floor to the bathroom so I'll need to slide the board behind the pipes..
how do you manage that with the dot 'n' dab? ( no counter tops on so height not an issue for sliding down.. )

drill small holes and use a mortar gun to squeeze it in behind?

 

[PrenticeBoyofDerry]

Are these the supply pipes for the dishwasher, they will or should be clipped. When you remove the clips, there should be some leverage to get behind pipes, so board should slide in okay.
With it being in the position it is you will not have match the board up to other boards so you can push board to the wall.
So Apply your adhesive to board around the perimeter and in lines of about 10inch apart.
Try get some in the area on the board where the pipes, then slide behind the pipes, spirt level, block of wood and a hammer to tap it up to wall and level it.
If it is a bit tight you could consider, cutting board. so joint is just above your pipe line 15 inch say apply that, then apply second board above it plenty of adhesive where the joint is, apply self adhesive tape and plaster finish.