Minimal Hakyll site

Question

I understand there's an example site given by

hakyll-init app

But I'm looking to reduce even more to the skeleton, and just have 1 markdown page that renders in the root, "localhost:8000/", and an alias "localhost:8000/index.html."

From the instructions, I have created this:

.
├── app
│   ├── app.cabal
│   ├── _cache
│   │   └── d5c19886a1234f571c624d44ba520d2b
│   ├── css
│   │   └── default.css
│   ├── images
│   ├── index.markdown
│   ├── _site
│   │   ├── css
│   │   │   └── default.css
│   │   └── images
│   ├── site.hs
│   ├── stack.yaml
│   └── templates
│       └── default.html

And I have the following in:

site.hs

--------------------------------------------------------------------------------
{-# LANGUAGE OverloadedStrings #-}
import           Data.Monoid (mappend)
import           Hakyll


--------------------------------------------------------------------------------
main :: IO ()
main = hakyll $ do
    match "images/*" $ do
        route   idRoute
        compile copyFileCompiler

    match "css/*" $ do
        route   idRoute
        compile compressCssCompiler

    match "index.markdown" $ do
        route   $ "index" + setExtension "html"
        compile $ pandocCompiler
            >>= loadAndApplyTemplate "templates/default.html" defaultContext
            >>= relativizeUrls

    create "/" $ do
        route   $ "index" + setExtension "html"
        compile $ pandocCompiler
            >>= loadAndApplyTemplate "templates/default.html" defaultContext
            >>= relativizeUrls

--------------------------------------------------------------------------------
postCtx :: Context String
postCtx =
    dateField "date" "%B %e, %Y" `mappend`
    defaultContext

This seems to compile:

app $ stack exec site watch
Listening on http://127.0.0.1:8000
Initialising...
  Creating store...
  Creating provider...
  Running rules...
Checking for out-of-date items
Compiling
Success

But when I load http://127.0.0.1:8000, or http://localhost:8000/index.html, I don't see my template, I see:

File not found

How can I fix site.hs for a minimal Hakyll (only an index.html created from a markdown stub), and how can I understand the debugging better? Eg, here I would have liked to see some kind of "stuff won't be found" at compile time. Where would I look for that?