I am trying to create a sliceform for the first time. I know my tree will not be very pretty, but please bear with me. I created a freeform body, and did the slicing command twice (in perpendicular directions). Then I just did a boss-extrude for each slice. I've colored the slices in yellow and blue in the normal orientation to more easily see.  

Now, my confusion is how to best go about creating the interlocking slots next. My understanding is that, Let's say the "Blues" will need slots starting from the top and conversely, the "Yellows" will need slots from the bottom to interlock, but I don't understand how to set this up or what commands/processes to use for this.  

 I would like this to be able to be FLAT-PACKED  and then assembled.

Thanks for your help! I appreciate it.