I used three layers of 5mm foam core glued together, then three layers of Minijumbuk Nu-Wool Quilt Wading on top of that, because I didn't have any batting. Before gluing the wadding layers to the foam core, I pre-drilled a series of holes as Jodi had done, for later tufting.
Next I covered the mattress with fabric. I didn't have any ticking in my stash, but I did have this pretty pink stripe which I thought would look okay.
After sewing the tufts, I made a bottom cover with cardstock. I didn't add and strip around the outside as Jodi did, because the mattress didn't appear to need it. It would also have made it difficult to add the fitted sheet and still have it sit comfortably in the bunk.
A big thanks go to Jodi for her inspiration and generous spirit, she made this project a whole lot simpler for me.