I will like to place the black box, with the number and the chapter outside of the line of the text. I will like place it 1 cm to the right.
\documentclass[oneside,10pt,oldfontcommands,standalone]{memoir}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{fix-cm}
\makeatletter
\newcommand\HUGEr{\@setfontsize\Huge{50}{60}} %used to set the number in chapter section
\makeatother
\usepackage{blindtext}
\usepackage{tikz}
\makechapterstyle{box}{
\renewcommand*{\printchaptername}{}
\renewcommand*{\chapnumfont}{\normalfont\sffamily\HUGEr\bfseries}
\renewcommand*{\printchapternum}{
\flushright
\begin{tikzpicture}
\draw[fill,color=black] (0,0) rectangle (2cm,2cm) node[color=white] (test) {};
\draw[color=white] (1cm,1cm) node { \chapnumfont\thechapter };
\draw[color=white] (-0.5,0) rectangle (-0.1,2) node[midway,rotate = 90,color=black] () {Chapter};
\end{tikzpicture}
}
\renewcommand*{\chaptitlefont}{\normalfont\sffamily\HUGE\bfseries}
\renewcommand*{\printchaptertitle}[1]{\flushright\chaptitlefont##1}
}
\chapterstyle{box}
\begin{document}
\chapter{Introduction}
\Blindtext
\end{document}
...\begin{tikzpicture}\hspace*{1cm}...