How to align the slash in the table?

Question

   \documentclass[12pt]{article} 

\usepackage[T1,T2A]{fontenc}
\usepackage[mathletters]{ucs}
\usepackage[utf8]{inputenc}
\usepackage[english,ukrainian]{babel}
\usepackage{ulem}
\usepackage{amsmath}
\usepackage{multirow}
\usepackage{slashbox}

\begin{document}
    \begin{tabular}{| c | c | c | c |}
        \hline
        \multicolumn{4}{|c|}{} \\
        \hline
        \multirow{3}{*}{\slashbox{}{}} & & &\\
        \cline{2-4} & & & \\
        \cline{2-4} & & & \\
        \cline{2-4} & & & \\
        \hline
        \multicolumn{3}{|c|}{} & \\
        \hline
    \end{tabular}
\end{document}

this is how the table should turn out, but there are problems with the dash in column 1. It seems to me something with the size, because when I increase this column, the line falls into place

Answer 1

Slashbox is rather old and undocumented. It's not in TeXLive. I use diagbox which has good documentation instead and does the same thing.

\documentclass{article}

\usepackage{multirow}
\usepackage{diagbox}

\begin{document}

  \begin{tabular}{| c | c | c | c |}
    \hline
    \multicolumn{4}{|c|}{}    \\
    \hline
    \multirow{3}{*}{\diagbox[dir=SW,height=4\line]{}{}} &   &  & \\
    \cline{2-4}                                         &   &  & \\
    \cline{2-4}                                         &   &  & \\
    \cline{2-4}                                         &   &  & \\
    \hline
    \multicolumn{3}{|c|}{}                              &        \\
    \hline
  \end{tabular}
\end{document}

Answer 2

Here is a way using nicematrix. Of course you can make any adjustments you need: column width, color, line thickness, etc.

\documentclass{article}

\usepackage{nicematrix, tikz}

\begin{document}

\begin{NiceTabular}{cccc}[hvlines]
\Block{1-4}{} \\
\Block{4-1}{} & & & \\
 & & & \\
 & & & \\
 & & & \\
\Block{1-3}{} & \\
\CodeAfter
    \tikz
    \draw (6-|1) -- (2-|2);
\end{NiceTabular}

\end{document}