I'm not a pro, but
1) the magwell should be perpendicular to the ground to allow the not-so-easy (w/dirty mags) exit of the mag when you press the button
2) for practice purposes, it's a good idea not to have a mag in the gun so that you can do more reloads in less time(just don't get lazy on the button press)
3) to try speeding up the first part you can do some Burkett reload, where on the beep you try to get the mag just to the edge of the magwell as fast as you can(w/par time)
what's your baseline time for the slide lock reload so that I can geta reference and improve mine