public class ExampleClass : EditorWindow
{
    public AudioClip exampleClip;

    [MenuItem("Example/Spell Builder")]
    private static void Init()
    {
        var window = GetWindow<ExampleClass>("Spell Builder");
        window.Show();
    }

    private void OnGUI()
    {
        exampleClip = EditorGUILayout.ObjectField(exampleClip, typeof(AudioClip), false);

        if (GUILayout.Button("Build"))
        {
			var assetName = "Do a string field like the audio clip example."
			var defaultPath = $"Assets/{assetName}.asset";
            var instance = ScriptableObject.CreateInstance<YourSpellClassDerivedFromScriptableObject>();
			instance.SpellActivationClip = exampleClip;
			var AssetDatabase.CreateAsset(instance, defaultPath);
			AssetDatabase.SaveAssets();
        }
    }
}