Imo core things normal folks do have to be: normal.

Shipping things takes a long time, and is done by caravan or ship. And it takes a long fucking time.

Taverns cost money. Long term places have rent or similar.

If people go on a journey they need supplies.

If people get wounded they take a while to heal, and might get sick.

People have generally (or consistently) normal lifespans, with younger years being fit and ready for anything, and older years slowing down, or not even being able to fight any more.

In my opinion acing those types of things means when you do introduce magic or other fantasy stuff, it is impactful and rare.

When I imagine Low Fantasy, there’s usually a House/Guild/Company that has one special person who bolsters their trade. Whether that special person has a magical affinity to trade, fight, vex, spy, or charm… even a single magical advantage, when applied consistently, could lead to market dominance.

For example:

• A successful and renowned caravan company has a magic-attuned fighter who can fend off thieves and ambushers, even if that means being the last alive.
• Local herbalist is suspiciously beating all of the competition. Upon further investigation, it turns out they hired a magic-attuned individual to charm their goods, evoking positive affect in customers.

You should implicitly define an upper boundary to how many people can have magic abilities, and to how often said people have powerful abilities. For example, say the nation that your story exists in has 100 million people, and each 100 million yields a handful of magical people. One special person is probably a baby, and two of them are probably quite old. A couple magical people might be quite powerful, another couple has quite mundane abilities, and perhaps one is somewhere in the middle. There may be more or less than a handful of magical people in the nation, since people may come to or leave from your nation.

Every magic item (even the more “common” ones) is valuable and treasured, even if it might not be used often

A +1 sword can split the hide of the toughest monsters and beasts, and is the heirloom of a powerful marquis

Three healing potions on the raised dias of the church, awaiting the arrival of the prophesied heroes, who will need them to vanquish the vampire

Or the duke with more money than sense, who has a small trove of magical items like the Stone of Gravity sensing or the Ring of Purple death detection. The twist is that in some forgotten corner of his room is a dagger that glows in the presence of demons (including the ones disguised as humans to overthrow the kingdom)

“Low Fantasy” is kind of a broad job description but I’d say besides GBU_28’s “normal people be normal” and TheOakTree’s “upper bounds on magic”, there seems tb be the one thing highly relevant enough to LF that it’s used to “sell it”:

It’s about human glorification.

Sure, there can be elves and dragons and stuff but the setting presents them as worse or lower than humans. For example, dragons are basically cats and can be domesticated, or elves isolate themselves because they are chronic backstabbers who can’t form any lasting alliance, let alone a nation or country. Or even worse: the dragons are cats and the elves are just basically cosplayer humans!

But in the end whatever races and species you add, it all ends up somehow being in the service of humans having the primacy on the setting.

Other than that, I’d say an important thing for making a world feel low fantasy is that it has to be easy to pick a cause to join or fight for. It’s a world that has, dunno, artists, bards, poets, scholars, radio talks, whatever, that makes easy for people to broadcast and pick on immediate needs, be they refuge, food, or protection from the Hourglass Demons.