In the past, I had these made for me by an upholder, but given the point of this particular bed was not only to look cheap-n-cheerful but also to be like that (and to save a lot of money, of course), and knowing I can’t sew beyond buttons, everything was made to be cut and glued as if it was just paper or thin card being folded.
First of all, cut the inner foam to size (a fine serrated bread-knife is ideal), making it a bit smaller to allow for the thickness of any fabric that’s to be used. Then lay it face down on the back of the cover (in this case a piece of satin) and fold over the ends of the fabric, pinning in place but not stretching so tightly as to distort the foam.
Now at each end in turn, lift the loose fabric out of the way and spray glue onto the foam, taking care not to go over the edges and on to other parts of the fabric (use a piece of card if necessary to mask off areas). Finally, smooth the fabric towards the middle of the mattress and ensure there are no creases; leave to set fully.
There are many ways to fold and tuck corners, so what is shown here is only the way I chose to do it; you may be happier doing it another way for aesthetic or practical reasons, but the principles should be similar.
First of all, pin everything ready for the inner fold, which will be 45° so that when the outer fold is completed, it will be flush with the end.
Iron a firm crease on the edge, move the pins back about 2cm and place some hemming tape between the surfaces, then iron together.
Repeat the process for the outer fold, by pinning and creasing, then sealing with ironing tape.
To finish that corner, trim off any excess and glue the middle part of the side piece.
Repeat on the remaining three corners.
A final tidy-up of the folds was achieved by turning the mattress onto its side and carefully ironing closed the open ends with hemming tape.
The bottom is a bit of a mess, and can either be left as it won’t be seen, or using yet more hemming tape, a scrap of fabric can be used to cover the joins, and it doesn’t even have to match the existing cover.
For the main bed-covers, a pair of cheap pashmina scarves were purchased (a fiver each or 3 for £10, so not exactly breaking the bank), then just folded in half and laid loosely on top.
And that’s it. Not much to look at, but then it wasn’t meant to be complicated.