Set Different Shipping Method for Each Order

[ninjacoder30]

I am able to split the order based on the Stock Status but the problem i am facing is when i am trying to set shipping method to the order.

Actually i want to set different Shipping Method to both the order.
e.g. first Order i want to set Shipping as free shipping and 2nd as Flat rate.

Below is the code used to set the shipping method for 2nd order but i am getting The shipping method is missing. Select the shipping method and try again.

$quote->getShippingAddress()->setShippingAmount($total)
            ->setShippingMethod('freeshipping_freeshipping'); 

Also Tried Below Code Same Issue. The shipping method is missing. Select the shipping method and try again.

use Magento\Quote\Model\Quote\Address\Rate

          $this->shippingRate
            ->setCode('freeshipping_freeshipping')
            ->setCarrierTitle($carrierTitle)
            ->setPrice($total);

        $shippingAddress = $quote->getShippingAddress();

        $shippingAddress->setCollectShippingRates(true)
                        ->collectShippingRates()
                        ->setShippingMethod('freeshipping_freeshipping');

        $quote->getShippingAddress()->addShippingRate($this->shippingRate);

Please Help