Sorry, but I'm not sure if there is a single framework that is easy for a beginner :) But from all above I'd choose Yesod. I have some expierience in web development in haskell (i made SaaS service to create and manage online stores with haskell -
alovendo.com). Unfortunately when I started it I also was a beginner and decided to build my own framework to get deeper understanding of what i was doing. Since then i reviewed existing frameworks and in my opinion Yesod has beautiful and powerful architecture with many options to customize it to your own needs. If i ever start another web project in haskell I definitely choose yesod.