I'm no teacher, but my first reaction is that the onus is on the student to be organized and motivated. But that's not helpful.
For organization maybe request that he have a music folder , keep his lessons in it and bring it every lesson. Reward success with slap lessons. Otehrwise stick to basics
I think the best motivator is curiosity, personally...it's what motivates me.
Maybe give him problems to solve on his own that would illustrate the lesson?
Here's a riff, see if you can notate it
Here's a notated riff, see if you can learn it
here's a riff in C, see if you can figure it out in G
here's a slap figure see if you can play it finger style etcetc