$coordinates = [
     'x' => 100,
     'y' => 60,
     'h' => 250,
     'w' => 250,
];

$field = StreamField::find(4);
$field->coordinates = $coordinates;
$field->save();

protected $casts = [
     'coordinates' => 'array'
 ];

$field = StreamField::find(4);
return $field->coordinates['x'];

$table->json('coordinates')->nullable();