If you want to use Evocation instead of Sponsored magic or Thaumaturgy, there are a few possibilities.
--You could telekinetically launch yourself (harry does this more than once) but the landing might hurt.
--You could telekinetically (via Air or FIrce) solidify wings and/or an airfoil. This would be pretty straightforward, but would require something analogous to an athletics or Driving role indicating that its just a tool and you still need to be skilled. This is really more like a magic hang-glider.
--If the character is a Force specialist you could let him fly Magneto Style, but Id want to make it notably difficult even for a specialist.
--where it My Character, Id probably go for a combination of Earth and Force or Earth and Air (since controlling Opposite elements is considered especially awesome). Basically it would happen in two stages: First use Earth magic to reduce your personal gravity until you basically float, then use air or force to provide movement and direction. From a conservation standpoint its only taking a fraction of the force as a cannon-launch would. Mechanically its balanced by the danger of loosing control while remaining in Float Mode, and that outside forces like wind will be extreme impediments, so its not as useful for long-term flights.