You can mark a dictionary directly for serialization. SaintsField will internally use SaintsDictionary to serialize it.

// Note the `partial`!
public partial class SerDictionaryExample : MonoBehaviour
{
    [Serializable]
    public struct Sub
    {
        public string subString;
        public int subInt;
    }

    // normal serializable
    [SaintsSerialized] public Dictionary<int, Sub> dictIntToStruct;
    // interface is also supported, just like SaintsDictionary
    [SaintsSerialized] private Dictionary<int, IInterface1> _dictInterface;

    // can be nested inside array/list, just like a normal serializable type
    [SaintsSerialized] private Dictionary<IInterface1, int>[] _dictInterfaceArr;
    [SaintsSerialized] private List<Dictionary<IInterface1, IInterface1>> _dictInterfaceLis;
}

Because it uses SaintsDictionary internally, if you want to receive the field value for OnValueChanged, you need to use IDictionary<,> or SaintsDictionary<,> as callback parameter.

[SaintsSerialized, OnValueChanged(nameof(ChangedWatcher))] private Dictionary<string, int> _myDictionary;

// Either `IDictionary` or `SaintsDictionary` type 
private void ChangedWatcher(IDictionary<string, int> dic) => Debug.Log(dic);