Bring a large pot of salted water to a boil. Blanch the green beans for 2–3 minutes until bright and tender-crisp, then transfer them to a bowl of ice water to stop cooking; drain and set aside.
Preheat the oven to 180°C (356°F). Pat the salmon dry and season both sides with salt and pepper.
Heat an oven-safe frying pan over high heat with a little vegetable oil until very hot. Reduce the heat to low, place the salmon skin-side down and cook 3–4 minutes until the skin is crispy.
Transfer the pan to the preheated oven and bake the salmon 8–10 minutes, or until cooked through to your liking; remove and keep warm.
In a small sauté pan, heat a little vegetable oil over medium-high heat. Add the crushed garlic and fry briefly (about 2–3 seconds) until fragrant—do not burn.
Add the blanched green beans to the garlic pan with the butter and toss for 1–2 minutes to heat through and coat; season with salt and pepper to taste.
For the salsa, finely chop the roasted bell pepper and baby spinach; mix with 1 tsp olive oil and season with salt and pepper.
Serve the baked salmon with the garlicky green beans and spoon the roasted pepper and spinach salsa on top or alongside.