Am trying to use up some scraps of upholstery fabric so cut six squares  and a strip for another door stop.

if you make with lighter weight material you will need heavy duty interfacing

method: fold the strip- about the same length as the side of a square –  edges to middle and then fold in half and straight stitch along the length on either edge to create a handle. Position the handle on top of the centre of one of the squares and sew the ends firmly with a quarter inch seam. This seam will be hidden later.

take four squares to form the sides of the cube. With right sides facing and a half inch seam,  fix them in a box shape then pin the top square facing downwards carefully to form the cube lid.

seam  the top to the sides, go slowly round the corners to catch all the bulk and keep a consistent half inch seam to fix the handles in place

check your work before pinning the bottom square in place, still wrong sides facing. Seam as the top but leave a gap for turning. Leave at least three fingers for your turning gap as the fabric is bulky.

check the seams at the corners and maybe go round again as the finished cube has quite a lot of weight to bear

turn Right side out through the turning gap in the bottom. stuff at least  two thirds of the cube with pillow stuffing (it will take more stuffing than you expect and you don’t want it saggy from understuffing) and then fill up with gravel, lizard litter or rice. Hand stitch the gap closed to finish.