200-350 is pretty short distance to worry about slope unless it's a super slow bullet or super steep slope. I'd suggest just using your phone for now to get the slope angle and pretty soon you'll have a solid feel for it and will know what to use. If you use a ballistic app then your issue is solved as you have the ability to run the slope from the phone and it uses that data to adjust your dial.
Also, as a tip. Don't adjust your distance, adjust your dial. For example if you are shooting 1000 yards and the slope angle math says shoot to is 950, it is wrong. You want to use the dial up and adjust it. So if the dial is 20 moa for 1000, 18 for 950, you actually will want to take 5% of the 20 moa dial which is 19 moa.