Grate the holes of the disk with the centre bit so that the screws will fit snug.
Glue the rubber bits to their positions.
screws fitted into the disk
Glue the rubber bits to their positions with epoxi glue
Rubber bits in position
Cut two parts from the strap band. They should easily go around your upper thigh and then have additional 10cm length.
Sew one buckle to each of the straps, keep its other end empty.
Test the straps in the disc on your leg and adjust their placement so that the buckle will be at a spot that it tightens around your leg.
Mark the places where the two straps overlap.
Punch a hole into the centre of the markings.
This will be the place where the centre screw of the disc will go through.
The strap band will stay in shape if you melt together the fibres of freshly cut ends (and holes), e.g., with a lighter.
Straps with attached buckle
Test strap position
Mark strap position
Glue the straps to the disc with Pattex Transparent. Apply glue on both parts and wait for about 10min. before putting them together.
Mount the Strap disk to the box.