You can create both Single DB or Elastic pool in free trial period. After 1 Month or if you use up all 200$ credit balance before 1 Month, after both cases, you won't be able to use the same resources and you will have to upgrade the subscription to pay-as-you-go
See free trial FAQs - https://azure.microsoft.com/en-in/free/free-account-faq/
Please don't forget to Accept Answer and Up-vote if the response helped -- Vaibhav
