Uneven placement of 6 subfigures

Welcome to TeX.SE! There are numerous possibilities to achieve something of this sort, here is one.

\documentclass{article}
\usepackage{multirow}
\usepackage{graphicx}
\begin{document}
\begin{figure}[htb]
\centering
\begin{tabular}{*{3}{@{\hspace*{1mm}}c}}
\multicolumn{2}{@{\hspace*{1mm}}c}{\raisebox{1.5cm}{\multirow{2}{*}{\includegraphics[width=6.2cm]{example-image-duck}}}}
&\includegraphics[width=3cm]{example-image-duck}\\[1mm]
& &\includegraphics[width=3cm]{example-image-duck}\\[1mm]
\includegraphics[width=3cm]{example-image-duck}
& \includegraphics[width=3cm]{example-image-duck} &
\includegraphics[width=3cm]{example-image-duck}
\end{tabular}
\end{figure}
\end{document}

The final choice of parameters may depend on the proportions of the images.

\documentclass{article}
\usepackage{graphicx}

\begin{document}

\begin{figure}[htp]
\centering

\sbox{0}{\includegraphics[width=0.65\textwidth]{example-image}}% The big figure

\begin{tabular}{@{}c@{\hspace{0.05\textwidth}}c@{}}
\usebox{0} &
  \parbox[b][\ht0][s]{0.3\textwidth}{
    \includegraphics[width=0.3\textwidth]{example-image}
    \vfill
    \includegraphics[width=0.3\textwidth]{example-image}
  }
\\[0.03\textwidth]
\includegraphics[width=0.3\textwidth]{example-image}
\hfill
\includegraphics[width=0.3\textwidth]{example-image} &
\includegraphics[width=0.3\textwidth]{example-image}
\end{tabular}

\end{figure}

\end{document}

The right column is made of two parts: the top one is a \parbox as high as the big figure, so the alignments are precise.