Centre belt below navel, equal length to each side.

Wrap ends round back...

... cross at the back...

... and bring ends to the front, adjust to equal lengths.

Pull left end across to centre...

... and cross right end over it towards the left.

Tuck the left-pointing top end under both layers of belt and upwards. Pull both ends horizontally to tighten.

Bring the left end down over the belt and cross the right end underneath.

Fold the top end underneath the bottom end and up through the loop made by the crossed ends...

... pull both ends horizontally to tighten...

... and you have your knot.