It’s easy to say the buckle end attaches at the 12 o’clock position but it’s not true.
The arrangement varies by brand, and by watch model within brands, or buckle type as you indicate.
Some straps are extremely short on one side and very long on the other.
Most have 5-9 holes; others have no holes at all; they fold around a buckle end.
Don’t even try to describe a how a conventional NATO strap fits in words.
Or the trim-to-fit rubber or leather straps that in effect “have no end”
Wear it however it feels best on your wrist.