How do I go about achieving a completely leveled face? (description in the picture)

Im using a Hafco milling machine at my school the rig is set up with an auto feed motor that only travels on one path, the other axis is manually adjusted.

I'm trying to manufacture a part for my project. however I can't seem to get the feed rate tuned in with the speed which the face mill cutter is rotating at.

is the feed rate how I go about achieving this goal or are there other aspects I need to consider to machine this completely flat.