More prelim and some modifications

 With the glue dry on the back wall seam, I applied some wood filler to fill the gap, because I think the join will be visible across the back of the rooms (depending on what covering I decide to use).

I'm going to add a proper window to the 'bathroom' area (which may become a study) - I have a House of Miniatures kit for a wooden sash window in my stash.  It made sense to align the new window with the kitchen bay, so I punched out the pieces for the kitchen bay roof to check that it wouldn't interfere with the new cut-out.  I cut a new window opening with a Stanley knife and metal safety ruler, which was hard work.  I filled in the remaining bathroom window by gluing the punched-out piece back into place (always save all your scraps with these kits).

I also cut the door openings wider in the central wall, to the size that will accept a standard commercial door (although I probably will leave the archway open on the ground floor.  To cut these, I got out the electric jigsaw for the main cuts and then finessed with the Stanley knife, which was easier than trying to do it all with a knife.  I realised later that I had forgotten to widen the door opening in the bedroom wall so I still have to do that.

Then it was time to start priming - I still have some artist's gesso left over from previous kits so I used that.  I paint it across the grain, so that it fills the grain a little.  I try to avoid getting it into the slots, and I try to avoid painting the tabs.  After the gesso dries, I will sand everything smooth with a palm sander.  It creates a good surface for subsequent painting, or wallpapering. I suppose technically I don't need to prime surfaces that will be covered by cladding or flooring, but at this point it's just easier to paint everything.  The white also shows up a lot of the flaws and pinholes in the wood, so I can fill them later if I need to.

The weights are holding down an extension piece that I glued onto the false bedroom wall - I added a 1 1/8" scrap of plywood from my stash leftover from building previous Greenleaf kits. The wider wall will give a little more room around the bed.