Draw up a basic idea of want you want the building to look like
It doesn't need to be as detailed as this one
Create a background to suit your building
This one includes the basic outline and the back of the "rooms"
Create half a floor grid, similar to tiles, with perspective
Copy the left half of the grid
Flip it horizontal
Add it to the right side
Add the floor grid to the background and choose a tile pattern
Notice the perspective is slightly more pronounced in the tile area. This is to give the feeling of parallax distortion when we add the front glass
Here I have added glass walls to the sides of the rooms
The "glass" windows are created with dark brown panels at twelve percent opacity
In this case I have justed added a shop counter to each room but you could add tables, chairs a TV or whatever you want
Add the front of the building, in this case a shop-front
Note that there is no "glass" in the front windows yet
Add some things in the front wondow
Such as shop items and signs
The flowers and cupcakes could have been added as furniture in step 7 by adding a "stand" of some sort
Finally ... add some glass to the front
The glass is made from panels of dark brown at twenty-five percent opacity
The only thing left is to add doors if required