Step 1:
Prefold and cut a large square in three parts of the same size. You can also use two smaller squares prefolded and cut in half, see picture below.

Step 8:
Fold this edge to the left.

Step 6:
Fold over these two lines

Step 11:
Fold over these two lines.

Step 10:
Turn the model

Step 9:
Fold in half over the white lines, then fold the left and right part downwards over the other lines.

Step 5:
Fold over these two lines, use the prefolded lines as guidance.

Step 7:
Fold over these three lines

Step 3:
Prefold in half, then prefold over the two diagonal lines.

Step 2:
Glue two (or three) pieces together into one long paper which is 6 times longer than wide.

Step 4:
Prefold, use the prefolded lines as guidance.

Step 12:
Fold over these four lines.

Step 13:
Press flat, see arrows

Step 14:
Add glue to the white marked edges and fold over the two blue lines.

Step 15:
Fold the edges backwards and open the sleeves.

Picture: Dollhouse Office made out of paper and Origami models

Done!
This is an Origami video tutorial for folding the jacket: