In a large pot, add water to lightly cover the pork belly—roughly 1.5 liters or as needed until the pork is just covered.
Bring to a boil over medium-high heat, then reduce to medium heat and simmer for 45 minutes until the pork is tender. Keep the pork warm in its cooking liquid.
While the pork cooks, peel the turnips and potatoes, and cut them into roughly thumb-thick pieces. Peel and dice the onions.
Heat roughly 3/4 of the lard in a large pan over medium heat. Add the vegetables and cook for 3–5 minutes, stirring occasionally, until they begin to soften.
Add roughly 500–750ml of the pork cooking liquid (stock) to the pan with the vegetables.
Season with salt, pepper, and marjoram. Simmer for 15–20 minutes until the vegetables are tender, creating a vegetable stew.
In a separate pan, heat the remaining lard over medium-high heat. Add the diced bacon and cook for 5–8 minutes until crispy and golden.
Cut the cooked pork belly into slices. Divide the vegetable stew among serving plates, arrange the pork slices on top or alongside, and sprinkle the crispy bacon over each portion.