Not sure which validation you're after but for example if you'd like to validate how many inputs are filled, as a quick test you could use this in your controller/route:

        Validator::extend('requireAll', function($attribute, $values, $parameters)
        {
            $countFilled = count(array_filter($values));
            return ($countFilled == count($values));
        });
        Validator::extend('requireMin', function($attribute, $values, $parameters)
        {
            $countFilled = count(array_filter($values));
            return ($countFilled >= $parameters[0]);
        });
        Validator::extend('requireMax', function($attribute, $values, $parameters)
        {
            $countFilled = count(array_filter($values));
            return ($countFilled <= $parameters[0]);
        });
        Validator::extend('requireBetween', function($attribute, $values, $parameters)
        {
            $countFilled = count(array_filter($values));
            return ($countFilled >= $parameters[0] && $countFilled <= $parameters[1]);
        });
        $v = Validator::make(Input::all(), ['time_slot_start' => 'requireBetween:2,3']);

        if ($v->fails())
        {
            return $v->errors();
        }

        return 'success!';

this example validates that 2 or 3 inputs are filled.

For a cleaner solution, I would recommend extending the Validator class and declare your custom rules and error messages in it For more info, see the validation in the laravel docs