I asked them that at several location- why do they always board people by rows 1 to 10, then 10 to 20, then 20 to 30, etc...
Because the second wave to board is always held up because the first wave is still seating itself.
Start from the back
I don’t know how much more obvious it can get: first in is the person who enters furthest from his seat. You seat the passengers in the waiting room accordingly; first person you want to enter, you preposition closest to the entry. When boarding begins, you keep seated at least half of the passengers, waiting to ask them to queue up to board until their standing wait will be less than a minute.For long flights, you could consider deliberately causing able-bodied passengers to walk for five minutes before boarding, just to improve their circulation and tolerate extended sitting.