Heat olive oil in a large sauté pan over medium heat. Add the diced slab bacon and sauté until the fat renders and the bacon is browning; about 2 to 3 minutes, shaking the pan frequently. Raise heat to high and add onion, garlic, and balsamic vinegar. Sauté until garlic is aromatic, about 1 minute more. Add apricots, raisins, and almonds. Sauté until almonds are toasted and the raisins are puffy, 2 to 3 minutes. Add spinach and sauté until deep green, tender, and softened; about 2 minutes more.
Drain mixture if necessary, and season generously with salt and pepper. Serve immediately.