It was a little tricky, mostly because you have to use tiny amounts of glue on some parts. I use a needle bottle (previously discussed here) and it went pretty smoothly. It’s a clever design.
It was also a bit fiddly because I chose to go with a fairly good friction fit on the slots. Not much margin for error and you have to align some slots semi-blind due to the way it’s assembled. I’ll admit to a bit of grumbling, but it all came together. If you’re committed to gluing every part then you could go with a wider slot and make assembly simpler, but I was trying to avoid glue where possible.
Irony: I ended up gluing almost everything. 
Yeah there’s just no good way to do that without an external editor and you can’t export catalog designs. This is why I use clones for my slots when designing things, I can easily resize the slots to accommodate different material thicknesses without scaling the entire design.
The good news is that I wanted the house to be smaller, so it all worked out!