[Ethereum] Create an ERC20 Stablecoin

erc-20ethersoliditystablecoinstokens

How to create a stable coin with an ERC20 token contract ? Does it require contract to be modified ?
Are there some good practices or standards ?

Stablecoins - regardless of the platform on which they've been implemented - generally fall into three broad categories:

Centralised / IOU : A centralised controller holds an asset and creates IOUs that can be traded back in for the asset at a later date. Ex: TrueUSD & Gemini Dollar.
Collateralised: Coin is issued in response to collateral being pledged. Value is kept stable by various means. Ex: DAI & Synthetix.
Algorithmic (also called Seigniorage Shares ): Value of the coin is kept stable by algorithmically expanding or contracting the supply of coins in circulation. Ex: Terra & Ampleforth.

Now, like any other ERC20 Tokens, you can build your coin based on its nature.