The sheets I found at Home Depot come 6 to a pack and measure 14.5" x 48" and cost $6.99. That comes to $1 a sheet !!! Remember this Diorama was initially created for Celebration V - for your own home version, you can if you prefer make a WIDER Hallway to say... fit your display shelf. You do have 48" to play with)

Start with a 16" mark on the bottom and Top of the sheet. This will be your Hallways' WIDTH.

Now cut along the 2 marks with your Utility knife. Make sure to have a NEW Blade, as this helps give you the BEST CUT. Styrofoam and Foamboard are the ENEMIES of Xacto Blades. Put the BIG sheet aside for the time being.

Using the shorter or the two pieces, you need to make a 8" Mark at the Bottom and Top of your sheet.

Take your Utility kinkfe and slice down your styrofoam.

You now have TWO pieces, The Bigger Bottom piece (16" x 8") will be your FLOOR. Now grab your Top piece...

... and measure 5.75" on the Left and Right TOP end

Slice this excess off with your Utility Knife. This will be your Wall. But first you must shorten the length...

Measure 14.5" at the Top and Bottom of the RIGHT side.

Now slice this chunk away with your Utility Knife. You should now have your Wall piece measuring 14.5" x 5.75"

Now go back to your Original BIG sheet.