Serializing a 2D array

I realize this question has been asked in the past but it has been at least 2 years and I’m praying that another solution has been found.

I have a game that is similar to chess and I’m wanting to make a Save Game option. The problem is the unit locations are saved in a Unit[,].

Is it true that the only way around this is to flatten the array or is there some other solution?

The thing with 2D array is they are still linear in memory.
Typically, you would indeed, flatten it into a a long stripe, then serialize it into sequence of bytes.

During Loading, re-construct 2D array from those bytes, just like you would any other entity.

Also, check here Serialize Multi-Dimensional Arrays

using System.Runtime.Serialization.Formatters.Binary;  
int[,] theArray = new int[2,3]={...};  
BinaryFormatter bf = new BinaryFormatter();  
MemoryStream ms = new MemoryStream();  
bf.Serialize(ms, theArray);