\begin{tikzpicture}[node distance = 3.5cm, auto]
  \node [start] (start_n) {Mix \qty{50}{\gram} flour + \qty{50}{\gram} water, stir};
  \node [block, right of=start_n, node distance = 3.5cm] (wait_n) {Wait\\ \qty{24}{\hour}};
  \node [decision, right of=wait_n, node distance = 3.5cm] (readycheck_n) {Ready?};
  \node [block, below of=wait_n, node distance = 3.2cm] (feed_n) {Feed the mixture };
  \node [decision, right of=feed_n, node distance = 3.5cm] (limitcheck_n) {>10 feeds?};
  \node [fail, right of=limitcheck_n, node distance = 3.5cm] (abort_n) {Discard all. Start over};
  \node [success, right of=readycheck_n, node distance = 3.5cm] (final_n) {Ready to use};

  \draw [line] (start_n) -- (wait_n);
  \draw [line] (wait_n) -- (readycheck_n);
  \draw [line] (feed_n) -- (wait_n);
  \draw [line] (readycheck_n) -- node {No} (limitcheck_n);
  \draw [line] (limitcheck_n) -- node (feedok_n) {No} (feed_n) ;
  \draw [line] (limitcheck_n) -- node {Yes} (abort_n);
  \draw [line] (readycheck_n) -- node {Yes} (final_n);

  \node [below of=feedok_n, node distance=2cm, align=left] (details2) [shape=rectangle, draw, fill=maingray]{%
    \textbf{Ready}: Mixture  has \emph{grown}, has \emph{bubbles}, and \emph{smells} vinegary/yoghurty. \\
    \textbf{Feed the mixture}: Discard all but \qty{10}{\gram}, mix in \qty{50}{\gram} flour and \qty{50}{\gram} water.
  };
\end{tikzpicture}