Cutting baseboard outside angle is different than cutting any 2x4 board because baseboards require immaculate cuts and clean edges. You’d have to cut outside corners for all four walls by setting the bevel at 45 degrees and the miter to 0 degrees. Mark the measurements on the baseboard using a pencil and cut the board keeping the front side a little bit longer than the backside to easily join the corner after everything has been cut. Take your time cutting so your corners don’t mess up and always test the fitting before you nail them.