While I don't know of or have found any open source Laravel Forex Broker websites, I can certainly point you in the right direction.
First I would suggest doing a Google search for your API provider + Laravel. For example this search first few results brings up some packages (paid and free) other users have created to integrate with the MetaTrader API: https://www.google.com/search?q=MetaTrader+API+laravel
From there I would suggest looking at the documentation of the plugin you choose (if you choose to use one or create your own) and look at the API documentation of MetaTrader API to see what options are available.
From there, you can build your own site with the features you want as needed. 😊