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$order = [
            'currency_id' => 'USD',
            'email' => 'email@domain.com',
            'shipping_address' => [
                'firstname' => 'John',
                'lastname' => 'Doe',
                'street' => 'Demo Street',
                'city' => 'Demo City',
                'country_id' => 'US',
                'region' => 'Illinois',
                'region_id' => 562,
                'postcode' => 60029,
                'telephone' => 9876543210,
                'fax' => '0987',
                'save_in_address_book' => 0
            ],
            'items' => [
                ['product_id' => '1', 'qty' => 1, 'price' => 100],    // simple product
                ['product_id' => '2', 'qty' => 1, 'super_attribute' => array(93=>52,142=>167)] //configurable product, pass super_attribte for configurable product    
    ] 
]; 

$this->createOrder($order);

public function __construct(
        \Magento\Framework\App\Helper\Context $context,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Customer\Model\CustomerFactory $customerFactory,
        \Magento\Catalog\Api\ProductRepositoryInterface $productRepository,
        \Magento\Customer\Api\CustomerRepositoryInterface $customerRepository,
        \Magento\Quote\Model\QuoteFactory $quote,
        \Magento\Quote\Model\QuoteManagement $quoteManagement,
        \Magento\Sales\Model\Order\Email\Sender\OrderSender $orderSender

    ) {
        $this->storeManager = $storeManager;
        $this->customerFactory = $customerFactory;
        $this->productRepository = $productRepository;
        $this->customerRepository = $customerRepository;
        $this->quote = $quote;
        $this->quoteManagement = $quoteManagement;
        $this->orderSender = $orderSender;
        parent::__construct($context);
    }

public function createOrder($order)
    {
        $store = $this->storeManager->getStore();
        $websiteId = $this->storeManager->getStore()->getWebsiteId();
        $customer = $this->customerFactory->create();
        $customer->setWebsiteId($websiteId);
        $customer->loadByEmail($order['email']); // load customet by email address
        
        if (!$customer->getEntityId()) {
            //If not avilable then create this customer
            $customer->setWebsiteId($websiteId)->setStore($store)->setFirstname($order['shipping_address']['firstname'])->setLastname($order['shipping_address']['lastname'])->setEmail($order['email'])->setPassword($order['email']);
            $customer->save();
        }
        $quote = $this->quote->create(); // Create Quote Object
        $quote->setStore($store); // Set Store
        $customer = $this->customerRepository->getById($customer->getEntityId());
        $quote->setCurrency();
        $quote->assignCustomer($customer); // Assign quote to Customer

        //add items in quote
        foreach ($order['items'] as $item) {
            $product = $this->getProductById($item['product_id']);
            $product->setPrice($item['price']);
            $quote->addProduct($product, intval($item['qty']));
        }

        $quote->getBillingAddress()->addData($order['shipping_address']);
        $quote->getShippingAddress()->addData($order['shipping_address']);

        // Collect Rates and Set Shipping & Payment Method

        $shippingAddress = $quote->getShippingAddress();
        $shippingAddress->setCollectShippingRates(true)->collectShippingRates()->setShippingMethod('flatrate_flatrate');
        $quote->setPaymentMethod('checkmo');
        $quote->setInventoryProcessed(false);
        $quote->save();

        // Set Sales Order Payment
        $quote->getPayment()->importData(['method' => 'checkmo']);

        // Collect Totals & Save Quote
        $quote->collectTotals()->save();

        // Create Order From Quote
        $orderdata = $this->quoteManagement->submit($quote);

        /* for send order email to customer email id */
        $this->orderSender->send($order);
        
        /* get order real id from order */
        $orderId = $orderdata->getIncrementId();
        
        if($orderId){
            $result['success'] = $orderId;
        } else {
            $result = ['error' => true, 'msg' => 'Error occurs for Order placed'];
        }

        return $orderId;
    }