Carpentry and Woodworking - Router question

I'm trying to put an edge profile on my a new sill and am having problems doing it on my router table. If I set the guide on the same side that i'm cutting when I come to the end of the board I get an uneven cut. Normally, I could set the guide on the side of the board opposite side that I want to cut but in this case its not even as the wall is not square. I know this has to be doable but I'm a novice with the router and can't figure it out. Any ideas ? Thanks

Yes, use a router bit with a roller guide built onto it. And run right to left on the table, keeping a firm grip on the left side pushing against the fence. The right side is for feed only, with only light pressure inward. Too much inward pressure, and you will snipe the end. If you are cutting end grain as well, cut it first. That way when you chip it out, and you will, the long grain run will usually fix it.