How about using a working variable like the following?

for (int wrow = numRows - 1; wrow >= 0; wrow--)
{
    var row = FlipVertical
                ? numRows - 1 - wrow
                : wrow;
    for (int wcolumn = 0; wcolumn < numColumns; wcolumn++)
    {
        var column = FlipHorizontal
                       ? numColumns - 1 - wcolumn
                       : wcolumn;
        Console.WriteLine($"{row} , {column}");
    }
}