How to create smart contract cross chain?

Smart Contracts
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1

I'm using the ERC721 model and I have a big question to be honest.

Considering an OpenSea model, how can I have a contract that I can sell NFT from several different networks?

How does this work in practice (in the contract's programming), does anyone have an example of this working to indicate a reading?

2

there are 2 options.
1: deploy the contract on two networks.
2: deploy it on one and you pay on the other. You need to have something Off-Chain to confirm the transaction. User send money to wallet A on chain A and you send the NFT from chain B to user.