Bring a large pot of salted water to a boil. Add the green beans and cook until tender, about 6-8 minutes. Drain and rinse with cold water.
In a small bowl, whisk together the mustard, vinegar, olive oil, and salt.
Pour the vinaigrette over the green beans and toss to combine. Top with the sliced almonds.
Notes
You can buy sliced almonds already toasted at most grocery stores, but if you can’t find them, you can toast your own. Just add them to a sauté pan over medium heat and toast for about 5 minutes until golden brown.