Heat a large skillet over medium heat. Add the sliced almonds and toast the, stirring frequently, until they take on a light golden hue, 2-3 minutes. Transfer them to a bowl and set aside.
Bring a large pot of salted water to a boil. Add the green beans to the boiling water and as soon as the beans are in the water set the timer for 2 minutes (don't wait for the beans to start boiling again). After 2 minutes, immediately drain the beans and put them in a bowl of ice water to prevent them from cooking any further. Drain and then blot them dry with a clean towel.
In the large skillet, melt the butter over medium heat. Add the blanched green beans and sauté them in the butter for 2-3 minutes until they're heated through and tender, but still slightly crispy. Add salt and pepper to taste. Drizzle the lemon juice over the green beans and toss them gently to coat. Transfer the green beans to a serving dish and sprinkled with the toasted almonds. Serve immediately.