Best way to slope shower tray waste pipe

[lost_diyer]

I’m installing a waste pipe for my shower, with the pipe running about 600mm to the center of the tray, where it will connect to the trap.

I’ve read a fall of 1 cm per every 40cm is adequate. What is the best method to ensure the correct slope has been reached for proper drainage?

I’m using solvent weld if that makes any difference.

I’ve attached an image of the existing waste which I’ll need to extend further.

 

[qwas123]

OP,
Your 10mm etc is fine but falls in narrow spaces often have to be whatever will work.
And yes, use solvent weld under floors & in walls.
More important, I notice a few things in your pic which suggest you get the shower tray on site so that you can "work from it"?
And you would probably be better off with bringing in a plumber?