Hakyll template list of rows

Question

I am moving my blog to hakyll.

In my webdesign at the index page there are horizontal rows with 3 post previews in each. Css/js is made in such a way, that I'd better populate this row not with all posts I have, allowing them to flow automatically, but I'd better cut posts list to chunks of 3 posts in each and generate separate row with 3 posts for each chunk.

So instead of

- row
   - col-sm-4 - col-sm-4 - col-sm-4
   - col-sm-4 ...

I want to have

- row
   - col-sm-4 - col-sm-4 - col-sm-4
- row
   - col-sm-4 - col-sm-4 - col-sm-4
...

In my site.hs I have quite typical

match "blog.html" $ do
  route cleanRoute
  compile $ do
    posts <- recentFirst =<< loadAll "posts/**"
    let indexCtx =
            listField "posts" postCtxWithCat (return posts) `mappend`
            favCtx

    getResourceBody
      >>= applyAsTemplate indexCtx
      >>= loadAndApplyTemplate "templates/default.html" indexCtx
      >>= relativizeUrls
      >>= cleanIndexUrls

And now I want to cut posts to chunks of 3.

    posts <- recentFirst =<< loadAll "posts/**"
    let postsBy3 = chunksOf 3 posts -- from split package

But how to feed this postsBy3 :: [[Item String]] further to template and how to use it... is a big question.

Just doing

listField "postsBy3" postCtxWithCat (return postsBy3) `mappend`...

is clearly a type mismatch.

Stuck.