Help please

[D-man]

Hey guys, im needing some help with mating in a new way to what im used to.

Basically, im needing to mate a "seat" inside a large dia pipe on an angle (Above the opening on one side and below on the opposite) that will be a seat for something else to slide into.



Im trying to get the image to the right mated inside the image to the left but on an angle (54 degrees) like the construction line.

Next post will be some images of exactly what i want to do

can anyone shed some light on the best way to do this?