% TOC title
\usepackage{titletoc}
\titlecontents{section}
    [15pt]
    {\bigskip\rmfamily\Large}
    {\contentslabel{15pt}}
    {\fbox{\hspace*{2.3em}\rule{2.3em}{2pt}}}
    {\titlerule*[1em]{}\contentspage}

\titlecontents{subsection}
    [35pt]
    {\rmfamily}
    {\contentslabel{25pt}}
    {}
    {\titlerule*[1em]{.}\contentspage\nobreak}

\titlecontents{subsubsection}
    [55pt]
    {\rmfamily}
    {\contentslabel{35pt}}
    {}
    {\titlerule*[1em]{.}\contentspage\nobreak}