How to Get Base URL of Default Website in Magento 1.9

Not too sure if you could use this interface.

As its scope related I will probably check the getBaseUrl from Magento/Framework/Url/ScopeInterface if I was you.

On top of that Magento tend to do the following to get the base URL of a store:

$this->storeManager->getStore()->getBaseUrl();

where _storeManager is Magento\Store\Model\StoreManagerInterface

So in theory (haven't tried it) what I would do is use this StoreManagerInterface to get all the stores via the getStores() method then use the code I pasted above to get the base URL for each store.

protected $config;

protected $storeManager;

public function __construct(
    ...
    \Magento\Config\Model\ResourceModel\Config $config,
    \Magento\Store\Model\StoreManagerInterface $storeManager,
    ....
) {
    ....
    $this->config = $config;    
    $this->storeManager = $storeManager;
    ....
}

Now you can use this like, but after creating website,group, and store

        $storeBaseUrl=$this->storeManager->getStore()->getBaseUrl();    
        $storeMainUrl = $storeBaseUrl . "CANBEANYTHING" . '/'; // replace "CANBEANYTHING" with your unique url
        $websiteId=1;// replace with your dynamic id            
        $this->config->saveConfig('web/unsecure/base_url', $storeMainUrl, 'websites', $websiteId);
        $this->config->saveConfig(
            'web/unsecure/base_link_url', '{{unsecure_base_url}}', 'websites', $websiteId
        );