Flash probably isn't the best tool to be using for a game, seeing as it's outdated and less than 2 years from not being supported in any major browser...
At this point for an in-browser game Javascript/HTML5 are probably the better choices.
I don't know what you mean by template but there are plenty of libraries/frameworks available for free that either support isometric features or are geared specifically towards creating isometric games; a simple Google search should return many results.
Goodluck.