Cut out 2 plastic circles from a thin plastic bag, like ones you get at grocery stores. (Don’t use plastic wrap.) Roll a piece of the masa in your palm into a ball about 1 1/2″ in diameter. Place one plastic circle on the bottom of the tortilla press and place the masa ball on top. Place the other plastic circle on top of the ball and press down the press to make a flat disk, jiggling the press a little as you get to the bottom (this makes a rounder tortilla). Open the press and check the tortilla for dryness and, if needed, add water to the remaining masa (the masa should be as soft and smooth as Play-Doh). Take the top plastic off, lift the bottom plastic with the tortilla in one hand and peel the tortilla from the plastic with the other hand.
Alternatively, you can place a ball between plastic sheets or parchment paper and roll the tortillas out with a rolling pin. They should be about 5″ in diameter and about 1/8″ thick.
Place the tortilla on the hot comal or skillet. Let it cook for at least 30 seconds (resist the urge to touch or adjust it). As soon as it can be flipped without sticking to the comal – it should be opaque on the side that it was cooking on. Flip with a spatula and cook for about a minute, until opaque and starting to freckle on the other side. If it is opaque but it has white-ish areas, you need to leave it a bit more, until those white-ish shadows become freckled with brown spots. Turn over once more, and now, after a couple seconds, tortilla should puff up like pita bread, if not all over tortilla, at least in an area of it. Let the tortilla cook still, for about 10 seconds, so that it cooks in between the area that puffed up.
If eaten that same day, tortillas may be kept wrapped in a clean kitchen towel or cloth. If not, wrap in a kitchen towel, inside a closed plastic bag and place in the refrigerator. They will keep for up to 3 days, afterwards they will turn too hard. Reheat in hot comal for 30 seconds or so on each side before eating. They can also be frozen and kept for months.