The moment I realized that we have the space for a window bench in our sunroom, I immediately envisioned a tufted French mattress as a cushion for the spot. Upon doing some research, I realized that having them made professionally can be quite expensive since it's such a labor intensive process. I'm not one to be deterred by a high price tag and realized that while there aren't too many tutorials out there for how to sew one yourself, it's actually a fairly manageable project. Here's how we did it:
Here is the mattress before it was tufted.
1. Cut the foam to size using a serrated knife, cutting halfway through the top, then flipping over to cut through the other side, yielding a straighter cut on the heavy foam. We cut our foam a bit larger, because you lose some size when you do the tufting. We lost about a 1/2" on either side.
2. Cut the batting to size for each of the six sides and apply the batting to the foam using spray adhesive. Use as heavy batting as you can find, as it helps bulk up the edge you're creating on the top and bottom.
3. Create a box cushion using this tutorial. Ignore the zipper instructions and sew the cover shut by hand. We left the long-edge on the back to be sewn shut by hand using a ladder stitch. In retrospect, we would have left a short-edge open to have less to sew shut. When cutting your fabric, add 1 1/2" to all sides for a seam allowance and to create some extra fabric for the tufting.
4. Once the cushion cover is done, you're going to start the welting: the stitch that runs across the top and bottom edges.
Take a long piece of thread and run through the sewing needle to make a very large knot at the end of thread.
Starting with the corner of the foam, pinch the edge where the top and side come together. About 1" down from the edge, stick your needle in from underneath. Pull the needle through the top, then stick it back down next to where the first thread came up and pull tight.
Stick the needle through the fabric and come out 2" over to the side.
Repeat the above steps and tie the string at the end. I followed this tutorial for this step. You're going to want to make the stitches as consistently spaced as possible, so that you can match them up vertically on the top side.
Once you've stitched all the sides, it's time for the tufting. Begin by mapping out where you want your tufts to go by using pins on both the top and bottom, spacing them evenly apart. We opted for approximately 7" spaces between our tufts, working with a 3x11 grid.
Using the 6" needle, double thread the needle with an effective thread length of 18". Choose a side to be the bottom and start there, pushing the needle through the back to the front and then pulling it back through next to the first hole from the front to the back.
Pull the needle all the way through to the front.
Push the needle back through to the back.