How to cut tall baseboard on a miter saw on the flat with an angle greater than 45 degrees?
Based on what you have said, the only way I can think to do this would be to create a jig that raises the angle of the baseboard to the correct angle. In this case you need to raise it by one degree. However, with a change that small I'm not sure how easy it will be to build the jig. 

What I would do is build a jig that raises it more. Depending on the miter saw, you should have some sort of bevel guide. Hopefully this is in degrees, but it may be just some preset notches with the degrees noted. Regardless, I would build a jig that raises it by either at least 5 degrees possibly 10 degrees (either way you will need to support the work piece, but the steeper the angle the more difficult to support. This would mean you would cut at 41 or 36 degrees. Depending on the precision of the equipment you are using, it may be easier to build the jig to either 6 degrees or 11 degrees and cut and set your saw to 35 or 40 degrees as appropriate.