Create a Contract, Mint Tokens, and List Them for Sale, All in One Place OpenSea’s Storefront Manager allows you to create a contract and an OpenSea Storefront, all without a single line of code. All you need is some content, a wallet, and a little bit of ETH to pay for gas. There’s no fee beyond what the Ethereum network charges.

https://medium.com/opensea/how-to-create-your-own-marketplace-on-opensea-in-three-minutes-or-less-12373ca5818a?s=09