Mix the hot water with the masa harina. Add it about 1/2 cup at a time, kneading and mixing at first with a fork, then your hands. You will likely need all 1 13/4 cups of water, but this will depend on how dry your climate is, and how old your masa harina is. You want a very pliable, almost wet dough that doesn't stick to your hands when you roll it into balls. Do a tester: Roll a ball of masa and then flatten it. If it cracks all over along the sides, you will need a bit more water; start with a tablespoon at a time. If it sticks horribly, add a tablespoon at a time of masa harina, mixing well after each spoonful.
Preheat a comal or griddle or cast iron skillet over medium heat. You want it less than 500°F, and about 350°F is best.
Form the masa into balls of about 45 grams, or the size of a golf ball. Pat them into fat tortillas, gorditas, between your palms. You want them about 1/4 inch thick or a little fatter. Nothing too thin yet.
Heat the gorditas on the comal. First side gets 1 minute. This will be the base of your sope. Flip and heat the other side for about 30 seconds.
Move the sope off the comal and use your thumbs and forefingers to form a lip around the edges of your sope on the side you just cooked, which will be more supple. Yes, it will be very hot. Push down the center of the sope a little so you have essentially a little tartlet. Repeat all this with the rest of the dough, setting aside the sopes for now. They can sit like this for several hours.
When you are ready to serve them, heat up a decent amount of lard or vegetable oil in a pan, enough to cover the bottom by about 1/4 inch. When it's hot, about 325°F to about 350°F, fry the sopes until crispy, which should take a couple minutes per side. You'll want to fill and serve them shortly after this.
Mix the dough as above and pat out those gorditas. Only this time, heat lots of oil or lard in a pan to about 325°F. You need enough for the sopes to float in the oil, so about 1/2 inch deep.
After you've formed the gorditas, use your thumbs and forefingers to form the rims on the uncooked sopes, rotating the sope as you go so it doesn't stick to the cutting board or table. Form all of them before you start frying.
Fry a few sopes at a time, starting cup side down, so flat sides up. Fry like this for about 2 minutes, then flip them. You will want to spoon hot oil into the cups immediately. You will see the insides bubble furiously, then calm down. When it calms down, remove the sopes to a cooling rack set over a baking sheet in the oven set to "warm." These can hold for up to 1 hour before serving. Any more than that and you will need to refry them for about 1 minute per side to re-crisp them.
Follow these tips for better sopes:
Have all the fillings made before you even start the sopes. Make the refried beans and whatever toppings you are planning ahead. For most people, you make sopes a day or so after you've made the toppings so all you need to do is reheat and fill.
If you want these as party appetizers, don't overfill or people won't be able to pick them up and eat them. If you plan on having people use a knife and fork, stack as high as you want.
Don't stack the sopes themselves, or they will steam and get soft... and you will be sad.
Broken or leftover sopes can be broken up and tossed in a stew. They're pretty great that way.
If you are using fresh masa, not masa harina, I do not recommend the all-frying method because fresh dough is wetter than dough made from masa harina. I've had more sopes explode and break when I do this. The comal method is best for fresh masa.