\documentclass[twoside=false]{scrbook}

\usepackage{floatlefttextright}
\usepackage{lipsum}
\usepackage{graphicx}

\begin{document}

\afterpage{\flblankpage}
\lipsum{100}


\addfig{
  \includegraphics[width=\textwidth]{example-image-a}
  \caption{Test figure}
  \label{fig:Test figure}
}

\end{document}