I have produced the following table with LateX, using the multirow and array packages. The final result is:
However, I noticed that the labels L1 and L2 are not quite vertically aligned with the entries $a_{11},a_{12}$, etc. Why is that? Is there anything wrong with my code (which has some code which was copied and pasted from other answers)?
\documentclass{article}
\usepackage{multirow}
\usepackage{array}
\newcommand{\nocorner}{1cm}
\newcommand{\corner}{6mm}
\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}}
\newcolumntype{C}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}m{#1}}
\newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}}
\begin{document}
\begin{table}
\setlength\extrarowheight{3pt}
\begin{tabular}
[c]{c C{\nocorner} C{\corner} C{\nocorner} C{\corner} C{\nocorner} C{\corner}}
& \multicolumn{2}{c}{$H1$} & \multicolumn{2}{c}{$H2$} & \multicolumn{2}{c}{$H3$}\\\cline{2-7}
\multicolumn{1}{c|}{\multirow{2}{*}{$L1$}} &
\multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{11}$}} & \multicolumn{1}{|C{\corner}|}{$c_{11}$} & \multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{12}$}} & \multicolumn{1}{|C{\corner}|}{$c_{12}$} & \multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{13}$}} & \multicolumn{1}{|C{\corner}|}{$c_{13}$} \\\cline{3-3}\cline{5-5}\cline{7-7}
\multicolumn{1}{l|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} \\\cline{2-7}
\multicolumn{1}{c|}{\multirow{2}{*}{$L2$}} &
\multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{21}$}} & \multicolumn{1}{|C{\corner}|}{$c_{21}$} & \multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{22}$}} & \multicolumn{1}{|C{\corner}|}{$c_{22}$} & \multicolumn{1}{C{\nocorner}}{\multirow{2}{*}{$a_{23}$}} & \multicolumn{1}{|C{\corner}|}{$c_{23}$} \\\cline{3-3}\cline{5-5}\cline{7-7}
\multicolumn{1}{l|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} & \multicolumn{1}{C{\nocorner}}{} & \multicolumn{1}{C{\corner}|}{} \\\cline{2-7}
\end{tabular}
\setlength\extrarowheight{0pt}
\end{table}
\end{document}



