You can serialize a two-dimensional rectangular array directly. SaintsField will internally use SaintsArray2DR to serialize it.

IMPORTANT: Set your MonoBehaviour/ScriptableObject to partial if the field is declaration inside. If it's inside a normal class/struct, you need to set all parent class/struct to partial

using SaintsField;
using SaintsField.Playa;
using UnityEngine;

public partial class GridExample : MonoBehaviour
{
    [SaintsSerialized]
    private bool[,] grid = new bool[2, 3];

    [SaintsSerialized, SaintsArray2DR(transpose: true)]
    private bool[,] gridHeightFirst = new bool[2, 3];
}