Start with two strips of Velcro, each 7.5 inches long. The hook strip is 5/8″ wide. The pile strip is 3/4″ wide.
These widths are for a watch case with 18mm spaces for the mounting pins.
The length is the diameter of your wrist. Adjust if different for you.
Feed the hook Velcro through the spaces between the watch case and the mounting pins. Have the hook surface “forward” so the hooks will be away from your skin.
Pull the hook Velcro so about equal lengths are above and below the watch case. Adjust later as desired. The hooks face “forward” so they will be away from your skin.
Press the pile Velcro strip down onto the part of the hook strip that is above the watch face when in reading position.
Wrap the pile Velcro around your wrist so it mates with the other end of the hook Velcro and holds the watch on your wrist. Cut off the extra length of pile Velcro.