One youtube video showed me how to play walking bass in the piano. Basically, you can just set a timer for 10 or 15 minutes, and metronome to a slowish tempo, choose a chord progression, and just walk with it until the timer rings. Apply as many concepts as you want to or can. Repeat in a different key or with a different chord progression. You can put a rootless voicing in the right hand, like a 3 and 7 or 3,6,9.
What this video, by Dave Frank, taught me is that a bass line is a melody. Since I can write melodies I can write bass lines.
The amazing thing is that after doing this with a few progressions, I found I could do it my head thinking of very precise notes rather than just vaguely. I did a 2/5/1 in Bflat and then in C, a blues progression in C, and then a 1/6/2/5. I also wrote a bass line for the A section of "Lulu's Back in Town."
I'm not good at it yet, of course, but I made very rapid progress, from barely being able to play one at all to being able to play one with some fluency. When I don't set a metronome I just continually speed up.
This will provide a different kind of left hand for my playing, as opposed to my usual block chords.