Line a colander with a triple layer of cheesecloth and set in the sink.
Bring the milk and salt to a boil in a large saucepan over medium-high heat.
Stir in the vinegar or lemon juice. Reduce the heat to low and cook until the milk curdles, about 30 seconds.
Pour the milk mixture through the cheesecloth and let the curds drain for 10 minutes.
Pull the edges of the cheesecloth together to form a pouch and twist the pouch to squeeze out as much liquid as possible from the cheese curds.
Place the taut, twisted cheese pouch between two large plates. Weigh down the top plate with a heavy Dutch oven, heavy cans or brick.
Set aside at room temperature until the cheese is firm and set, about 30 minutes.
When the cheese is a firm block, cut it into 1-inch cubes. At this point, the cheese can be refrigerated in an airtight container for up to 1 day.