In the bottom of a Dutch oven, crockpot, or Instant Pot, spread half of the brown sugar, half of the crushed pineapple, and half of the cinnamon.

Set the ham on top and gently separate the layers. Rub the mustard over the ham. Spoon the crushed pineapple over the top and work it into the slices. Add the brown sugar and sprinkle with the remaining cinnamon, then pack it on.

For the Dutch oven: preheat the oven to 300°F (150°C). Prepare the ham as directed inside the Dutch oven; if the lid does not fit, cover with foil. Bake about 2 hours, until the center of the ham reaches 110°F (45°C). Transfer the ham to a serving platter to rest. Meanwhile, set the Dutch oven with the leftover brown sugar–pineapple mixture on the stovetop over medium heat. Simmer over medium-high heat about 15 minutes, stirring often to prevent burning, until the sauce is reduced, glossy, and slightly darker. Pour over the ham before serving.

For the crockpot: prepare the ham as directed inside the crockpot. Lock the lid and cook on high 3–4 hours (3 hours for a 6 lb ham, 4 hours for a 10 lb ham, 3.5 hours for anything in between); the center should reach at least 110°F (45°C) since the ham is precooked. If the ham is too large for the crockpot, replace the lid with a few sheets of foil. Once done, place the ham in a serving dish and pour the remaining juices into a large saucepan. Simmer over medium-high heat about 15 minutes, stirring often to prevent burning, until the sauce is reduced, glossy, and slightly darker. Pour the saucy glaze over the ham before serving.

For the Instant Pot: prepare the ham as directed, but when locking the Instant Pot lid, leave the venting knob "ON". Press the slow cook button on high heat and set the timer for 3 hours. Let the Instant Pot natural release, then remove the lid and place the ham on a serving dish to rest. Meanwhile, press the simmer button and simmer the pineapple–brown sugar sauce for 20 minutes, stirring often, until the glaze is thick and syrupy. Pour the sauce over the ham before serving.