make form in modal is centered

How can I make form in modal is centered?

What i've tried:

Checkbox::make('tandai')
    ->label('Tandai palsu')
    ->extraAttributes(['class' => 'flex justify-center']),

Checkbox::make('tandai')
    ->label('Tandai palsu')
    ->extraAttributes(['class' => 'flex justify-center']),

Checkbox::make('tandai')
    ->label('Tandai palsu')
    ->extraAttributes(['class' => 'flex justify-center']),

Checkbox::make('tandai')
    ->label('Tandai palsu')
    ->extraAttributes(['class' => 'flex justify-center']),