The first cut I'd make would be on a table saw, to make the step at the top of the long slope - a simple cut 0.25" deep while the plank is still square. You could also do it with a router or even hand-held circular saw, both guided with a fence of course.
For the short slope, 1" to 1.5" part, table saw or bandsaw would be easiest, followed by careful belt-sanding at slow speed with the mildest grit belt you can get, to the finished dimension.
For the slope leading to the 1.25" dimension at the step, where presumably the door stops, I'd use the table saw ideally, but you could do other things.
You could achieve both slopes with a router jig, or rough-cut with a table saw and finish on a router jig. I'd make the jig square, and make supporting wedges to hold the workpiece at the angles you need, it'd be easier than making an angled jig.
Edit: Sorry - just re-read your post about your saw's limitations. Take off whatever the saw can take, then make successive vertical cuts into the waste, remove the rest with a router jig as I've suggested.
Last edited by JCJCJC; 12-09-2012 at 04:11 PM.
Reason: lack of concentration ;-)