This is my dollhouse for which I created most of the contents. I built it from a Corona Kit named "The Aster Cottage." You can buy the kit from Greenleaf Dollhouses, here. The house is a little house in the real, big world - hence no miniature trees or flowers; a cradle made out of a real walnut shell; and a real bird's nest wedged between the chimney and roof, nestled in the full-sized ivy.
I did some "kit bashing" by eliminating the access opening to the loft (to make more room for the bed), and moving the ladder to the front (I didn't use their stairs), thereby freeing up wall space on the main level. I didn't use their detail for the top of the chimney, preferring to make my own out of rocks.
First of all, you need to work with dried twigs. You can dry them carefully in an oven - at about 200 - 230 degrees. Or just let them dry somewhere warm naturally. You can strengthen your twigs with a product by Minwax called wood hardener - available in most hardware stores. It is great stuff for working with fragile natural materials. You mix it 50/50 with acetone.
For your glues, use tacky glue (thicker and less runny than regular white glue) and Zap-A-Gap glue. It is a super glue, but you can also use it to fill any gaps between the joint of two irregular surfaces.
Get the spray accelerant that the Zap-A-Gap company makes too. This, when squirted on the wet glue joint, will *instantly* bond the glue. It is amazing and really helps. You can't easily clamp or tape twig things while waiting for the glue to dry.... You can get this glue and accelerant from any good miniature store. Earth and Tree ships anywhere and they give great service.
If you have bad or messy glue joins to hide, you can paint the glue with a mossy green-brown colored paint, or glue bits of moss or tiny dried flowers over it: use your imagination!
To make to scale sizes, I recommend you measure real furniture and then divide your figures by 12 for the 1/12 size. You can also use an inexpensive dollhouse doll and see if the doll fits.... or have regular dollhouse furniture in front of you and hold up your twigs to each section as you build.