Help, I can't figure out how to make this cut

[dennis thompson]

I am making a birdhouse which is in the shape of an octagon (from a plan from Woodsmith). The roof consists of 8 sections, each 3" across the top and 6 3/16" across the bottom, (think of a triangle cut off across the top). The roof sides are beveled at 11 degrees so they fit together when placed above the sides of the birdhouse.It is not a flat roof, The top of the roof is about 1 1/2" higher than the bottom. In addition there are decorative horizontal lines placed every 1" across the triangle about 1/8" deep.. I have made several test cuts and all of the turned out wrong. I know I have to angle the saw blade (11 degrees according to the instructions) and and angle my miter gauge (70 1/4 degrees according to the instructions) but how? What would the steps to the cut be? I went to bed thinking about this and woke up this morning at 5 AM thinking about this. How do I make this compound angled cut? I need some sleep:)
Thanks

[Bradley Gray]

Make the 1/8" deep cuts first across square stock.

Rip and cut to length rectangular blanks. Draw the angle cuts on one piece.

Make a simple 1 runner sled out of 1/4" ply with blocks to position the blank for the first 11 degree cut.

Make a second sled to make the last cut.

[dennis thompson]

Make the 1/8" deep cuts first across square stock.

Rip and cut to length rectangular blanks. Draw the angle cuts on one piece.

Make a simple 1 runner sled out of 1/4" ply with blocks to position the blank for the first 11 degree cut.

Make a second sled to make the last cut.

Thanks, I'll try that