Here's out it works...
Said person (A) walks in to store (Larrys Boot Shop in this case (person B)) at prearranged time (really helpful with Larry)
They shake hands and small talk. They then discuss what person A wants from their boot and what they'll be using their boots for. You might get offered a drink.
A takes their shoes and socks off. They were considerate, washed their feet before coming. Nice.
B then looks at A's feet, measuring the feet, analyzing the width the instep height, heel cup size, ankle bones, achillies width and calf width/size amidst other things, any random burrs/corns or things that could affect boot comfort and recommendation.
notice that bit, Person B will recommend person A boots, the boots that best fit your foot and needs.
B will walk away and come back with a choice of normally 2-3 boots, generally 1 he knows will not fit As foot well, it's to make the choice easier. A will likely wear all 3 boots for 15minutes, pacing around the shop flexing them as naturally as possible.
A will know which feels better, be abel to talk about which one feels better, any sore spots or things that aren't quite right like heel lift.
B will make the boot fit A best, knowing about their corns/unusual bits that will cause rubbing. These will then be worked out.
More than likely B will fit A for custom footbeds, unless A brought their own with them or is a fool.
Lastly A pays B, they shake hands and B knows that A is in the right boot for their foot and not what they wanted to fit... A also thanks god they didn't have a preset boot in their mind before going to see B as after their first 10days on snow, they couldn't be more stoked.
Moral = Don't have it set in your mind about which boot you'll be fitted in. Big mistake.