My urban fantasy setting, in which mythical creatures live in secret amongst the human race in the late 90s USA, has a species known as snow elves (my setting's take on Christmas elves) who are capable of creating portals from one location to another, and I'm trying to work out how this secret society would elect to set up their portal transportation networks given these portals' rules and limitations, which are as follows:
By laying their hand on a flat, reasonably-smooth surface, a snow elf can mark that surface as the center point of a portal. They can mark two surfaces at a time, one with their left hand, and one with their right. Once they have marked two surfaces, they can open and close a portal between them at will with a thought, from any distance, at any time, and can make it any diameter between 6 inches and 10 feet, providing the surface is large enough to fit such a circular portal.
The surfaces will remain marked until either the snow elf marks new surfaces, or the witching hour begins (which is at 4:00 AM GMT), which in addition to disrupting portal marks and a great deal of other magical energies, causes time to stop for an hour for anything non-magical.
The main takeaways from this are that 1: you need one snow elf for every connection between two places, 2: either the snow elf or an object they have marked needs to physically get to the location they want to make a portal to, and 3: whatever portal network they set up needs to be re-built from scratch every day.
Beyond that, immortals also have access to human society's methods of transportation (and there are enough immortals who can pass for human that they can use these with little issue).
With these facts in mind, the first thing I'd like to work out is the ideal structure for these portals. How they would arrange the locations of these portals to maximize ease and speed of daily setup, and allow a user of this portal network to get to as many places as possible as conveniently as possible, with as few snow elves needing to be employed as possible.
What would be the ideal framework for this network of portals?