Prepare all the ingredients: trim the green beans (cut off just the woody stem, you don't need to cut off the other end), cut the shallots into small cubes, finely chop the garlic, zest, and juice the lemon.
Cook the green beans: add the trimmed beans into a pot with very well-salted boiling water. Cook the green beans until they are soft but still very crunchy (they should squeak a little between your teeth). This will be 3.5-4 minutes for very thin beans, 4-5 min for medium beans, and 6-7 minutes for thick green beans. If you're using thin frozen green beans, cook them for about 2 minutes. Take one green bean out of the water (the thickest one) and try if it's cooked to your liking. When the beans are cooked, drain them and rinse with cold running water (or add to an ice bath - cold water filled with ice). Set aside.
Make the almond garnish: Add the almonds in an even layer to a big frying pan. Toast them in a dry pan until lightly golden (medium-high heat). Add the butter and the shallots, cook for about 2-3 minutes, stirring from time to time, until the shallots are soft. Add the garlic and lemon zest, cook, stirring, for about 30-60 seconds, until the garlic is fragrant.
Assemble: Add the cooked green beans and briefly warm them up with the sauce. Take the pan off the heat, add the lemon juice, and toss everything together. Season with salt to taste, if necessary.
Enjoy!