Filtering and sorting strings from a collection based on a condition

In the class, two properties are declared:

• SourceList – the initial set of strings, for example: {"string", "string2", "string3"}
• ResultList – should be filled with elements from SourceList that:
  1. Start with the letter s;
  2. Are sorted in descending order. It is required to implement the Method1 method, which will form ResultList according to the specified rules.

public class SomeClass
{
    public List<string> SourceList { get; set; } = new List<string>() { "string", "string2", "string3" };

    public void Method1()
    {
        var filtered = new List<string>(SourceList);
        // filtering and sorting logic should be here
    }
}