Vignette setting from foamcore tutorial

I like these because they're simple and inexpensive to make as I use foamcore from Dollarama at a cost of $1.50 per sheet.  There are no visible joints from the outside, and because of the way they're constructed the joints have glue on two sides rather than just one.

This one is 5" x 5" x 8" high. I use it mostly for taking pictures of new purchases.

This is a birthday card I made for my mother years ago. It's 5 1/2" x 5 1/2" x 8" high.

Decide how wide you want a wall to be and double that measurement. That will be the length of your first piece of foamcore and the width will be your chosen height of the wall. A second piece of foamcore will be a square the width of the wall. i.e. for the first one shown above, you will need one sheet of foamcore 10" x 8" and a second piece 5" x 5".

This one will have 10" walls that are 9" tall. 

Cut a sheet of foamcore 20" x 9"

Being very careful not to cut through the bottom cardboard layer of the foamcore,
Cut a vertical line down the middle of the sheet at the 10" mark. Then cut another vertical line 3/16" to the right of that line. After that cut a line across the bottom of the piece 3/16" from the bottom.

Using the tip of the X-Acto knife, carefully glide the blade along the bottom layer of the cardboard to release the foam and the upper layer of cardboard. If any foam remains, it can be scraped off with the blade.

NOTE: If you end up with bits of foam flying around and/or sticking to your knife, etc., grab a dryer sheet (such as Bounce). You can use it to wipe up the foam then it can be emptied into the wastebasket.

Now fold the foamcore back on itself along the vertical cut on the left. This will leave five layers: cardboard, foam, cardboard, foam, cardboard. You will need to carefully cut through the foam on the right hand side of the second layer of cardboard.

 

That will leave an opening in the middle of the sheet...

Like this. Insert glue along the vertical opening and fold the left side of the foamcore into the opening,

If you have a corner clamp, apply it and let the glue set.

If you don't have a clamp, you can place it in a gluing jig with a book to hold it in place until the glue dries.

While the glue is drying, cut a 10" x 10" piece of foamcore.

Once the glue has dried on the first piece, put glue all long the cut out section along the bottom and glue the square in place. 

Once that was done, I turned the piece upside down and weighted it with my gluing jig to keep the floor in place.

And here's the setting, ready for flooring.