Ideally, this part would be made on a 5 axis machine but not everyone has one of those. So, I would rough it out with ballnose endmill (a) and finish it with ballnose endmill (b).
The size of the part would be helpful in establishing the diameter of the endmill to use.
Use 3D jobs, one for roughing with a surface offset of (say) 0.15 and a second ffor finishing using a Constant Z strategy. If you have the HSM module, use that as it has a really good Adaptive Stepdown facility.