I found that some of the greatest teachers are the clips on the internet of people like Jessica Mendoza where she outlines, very simply, the fundamental mechanics of slapping, drag bunting etc.
My advice, as a parent of a 15 y/o .500+ lefty lead off hitter, is to make sure you teach the fundamental footwork for each different swing.
Have your DD watch some clips, then create some simple guides in your garage/basement that give reference points to the important things such as 'straight line to the pitcher, inside line of the batters box (my DD uses the same line for both so she knows if she is leaving the batters box) and, very importantly, the starting point.
here's a simple example:
Starting point
__________________X
Start with back foot on the X EVERYTIME!!! Our experience has proven that Slapping/Dragging are about timing. Practice stepping towards the pitcher from the same spot each and every time to create the timing memory.
My DD did countless reps with a bat in her hands without ever swinging. She remained loaded and ready to swing, but didn't until she could go through her foot work at full speed with a ball coming at her.
Once the footwork was down pat for drag's and slaps progression we went to hand and swing work. She started hitting off a tee, then hitting 'live balls' off of pitching machines, soft toss etc. One of the best tools we came up with was to set up 'gates' for my DD to hit in between (something as simple as two old ****** cones, or a glove and a visor) that were set up in the 5-6 hole about 4-5 feet apart. I challenged her to see how many slaps out of 10 she could get in the 'gate' until she consistantly hit 9 or 10 through repeatedly. Muscle memory....We move the gates to the different 'sweet spots' for slapping so she learn the body and swing muscle mechanincs to hit to the various 'gates'. Muscle Memory....
The combination of solid fundamental footwork paired with a simple 'target' to hit helped my DD immensely. She is far from perfect, but she can get the job done.
My simple advice to her has always been: get the ball in play and make them get you out.
Good Luck! Hope this helps a little.