Heat butter in a large saucepan over medium heat.
Once melted, bring the heat to low.
Cook the frozen green beans as per the package directions.
Add the slivered almonds and let them cook in the butter, stirring occasionally, until golden brown. (Approx. 5-7 minutes).
Once the green beans are cooked, add them to the saucepan with the almonds and toss to coat. You can add a wee more butter if needed.
Season with kosher salt and ground black pepper.
If you wish, squeeze from fresh lemon juice over the green beans as well.