Let's see if I can describe this without pictures. The buckle has 2 loops - the inner loop is sewn to the belt and the outer loop is the other. I see 2 ways to thread the tail...
1. Thread the tail through the inner loop and then through the outer loop (think Wilderness Frequent Flyer).
2. Thread the tail through the outer loop only, letting the velcro do all the work.
What are you experts doing?