I freeze the lemon juice in 1 or 2 teaspoon measurements in ice cube trays. That way I can make anything that requires a small amount of juice. Just defrost a cube or two before using. If I’m making soup, I don’t even defrost the cube, just throw one in the pot.
Large, flat crystals.
It’s not just that it’s larger, it’s that it’s larger and flatter. The flakiness of the salt is important: there’s nothing worse than a table-salt-rimmed margarita. Bits of it always fall off into the glass and collect in the bottom.
Even so. Small crystals still have more surface area per unit volume, unless the flat crystals are thinner than the small crystals; then you have to consider doing the math.
A common point of confusion. “Kosher salt” is not “salt which is kosher” but rather “salt which is used for koshering.” Koshering in this case could be loosely defined as preparing meat so that it is ritually pure. A particular kind of called colloqially known as Kosher salt, is used in this process. As you may have gathered, some people prefer it for cooking… and especially margaritas. 
Well I know that now…
One brand of kosher salt is made by putting normal salt through rollers so, yes, it would be flatter. But the point is not really the surface area/mass ratio, it’s that kosher salt sticks much better to meat because it has a large, flat area to adhere to.
It’s salt that was killed and slaughtered according to strict procedures and under rabbinical supervision.
Actually, I imagine one could just regular old table salt in a recipe like this, right? Maybe adjust the amounts downward a bit because the granules in generic Morton’s or whatever are smaller than the box of kosher salt I have. The added iodine in generic salt is the only real chemical difference, IIRC.
Back to the subject at hand, lemon meringue pie and the lemon jellies fail the “must be able to keep” test. I doubt I could make meringue in this vile humidity anyway and the jellies would get so humiidified they’d just be balls of slime.