For RPC calls to an Odoo database in Flutter I suggest to look at the Odoo RPC Client Library (https://pub.dev/packages/odoo_rpc). Personally I have good experience with this library. Using this library, a simple RPC call would look something like this:

var res = await client.callKw({
  	​'model': 'res.users',
  	​'method': 'search_read',
  	​'args': [],
  	​'kwargs': {
  	​	​'context': {'bin_size': true},
        	​'domain': [],
        	​'fields': ['id', 'name', 'email'],
        	​'limit': 80,
	​},
});

I hope this helps!

rpc