Artwork on 1 of X is web based. You are free to use any web based framework. You can also choose to design your artwork without a framework. If it runs on the web, it'll run in 1 of X.
There is only one real requirement for your artwork. It must use some sort of randomness. This way when 1 of X mints your tokens, they are different from one another. Otherwise they would fungible.
Optionally you can add features to your NFT. Features describe the token. These are used for filtering on many marketplaces. See this sketch for an example.
Create a Zip file containing an index.html file and upload it to 1 of X. After uploading you'll be able to view some sample tokens and give your collection a name, description, and a max supply.
When you're ready to publish, you'll submit your project to the blockchain and 1ofX will begin lazy minting your tokens.
On 1 of X, every token is lazy minted and the metadata is immutable. This means tokens will not change after they are purchased. For this to work correctly, 1 of X will create each token's metadata before it is sold. The metadata is what links your token on the blockchain to your artwork. Collectors will be able to see tokens before they are purchased.