You are allowed to use Flaticon images as the main element of the final product if you are working for one specific client and you won't be allowed to use the same image again for another project/client.
Please note that you cannot sell a product to a client who will be reselling the product to multiple clients if Flaticon resource is the main element of the composition.
For example, if you are a freelance designer and a client asks you to design a website, a business card, a flyer or a poster, you can use our images as main element for this specific client, but if the client asks you to design a t-shirt to be sold at his t-shirts store, you need to use our images as secondary element in that case.
When using Flaticon images, please note that you can edit it and give your client the printed product or the PNG/PDF file, but never an editable file which includes our resources.
If you download Flaticon resources as a free user you must include the attribution line on the products you are willing to sell and on your website. In case you don't want to include this attribution line, you must purchase any of our Premium subscriptions.