If you know some scales, use those + the octave slaps and move up and down etc. I came up with my own slap bass part but used no octaves, most do however. It's heavy on feel. Takes time to get the thumb and fingers to cooperate, but persistence pays off.
Try hitting the lower octave 2x with the thumb and the top 1x(RHCP's higher ground for the most part) plucking.
Lighten it up, turn the volume up and increase speed.
In a few days/weeks, you'll be doing it pretty well.
Try 3x thumb on the lower and 1x pluck on the top, then 1:1, 1:2, 1:3 etc and other combos to get use to things. Do not keep using the same old thing over and over, you already learned that, so try something new to learn.
You can also pluck the 5th instead of the octave, and the 5th and the octave if you want to add 1 pluck per string with the index and the middle. Many combos to try. Gets crazy, but it becomes pretty easy over time.
Video Youtubes are very good for many things.
I learned double thumbing from Victor Wooten's you tubes.
Now I hardly do much but a flurry of notes coming out of the bass, people think you are good etc(ha!).
Try figuring out a new simple slap bass part each week or each day etc from Youtube. In 1-2 years you will be very good if you do that routine.
Nice thing is that many bassist are very motivated to learn and play this style, so it keeps them practicing and playing! Time on the bass and good focus will make you a much better player, but we all need some motivation.
Use it!
Tom
