Well most of what's going on is most likely just because you are new to slapping like you stated. As you get more comfortable with the style/technique the phrasing will smooth out.
There are a few ideas I CAN give you to work on your slap playing/phrasing in general. One would be to take some phrases you play and think of them purely as rhythms. From there experiment with the actual pitched notes you play. Don't use the same notes. Take that phrase and keep changing the notes. This gets you hearing the phrase differently and it's no longer one lick/groove. It becomes an idea that evolves.
Lastly, an idea I use quite a bit is to take a particular phrase and use the idea of note displacement. This is another way to take a phrase and create new ones. An example would to be to take a phrase, say a 8th note feel slap groove in 4/4. Play that phrase say 4 times and each time start in an 8th note later than the previous measure. This constantly changes the phrase AND you get used to hearing it on different beats. Actually writing these phrases out makes it a lot easier to play and see.
These ideas will help get you out of the rut of just connecting learned phrases together and get you away from that "mechanical" sound of phrase 1 to phrase 2, etc.
Let me know how it goes!
