I am trying to create a document in latex but I am having difficulties with the chapter location.
On each page of my document I want one chapter, but I want to have it in the top left of the page. However, in my attempt there seems to be a big white gap.
Below is a screenshot of what I am seeing

Here is my code:
\documentclass
[oneside,landscape,tikz,border=2pt,png]
{book}
\usepackage{xcolor}
\usepackage{blindtext}
\usepackage{tikz}
\usepackage{smartdiagram}
\usepackage[absolute,overlay]{textpos}
\setlength{\TPHorizModule}{1mm}
\setlength{\TPVertModule}{1mm}
\usetikzlibrary{shapes.symbols}
\tikzset{sequence item/.append style={
/utils/exec={\ifnum\xi=1
\tikzset{signal from=nowhere}
\fi
}
}
}
\usepackage[left=0.2in,right=0.2in,bottom=0.5in]{geometry}
\usepackage[
automark,
autooneside=false,
markcase=noupper,
headsepline,
headwidth=\the\textwidth+12mm:-5mm,
]{scrlayer-scrpage}
\clearpairofpagestyles
\rehead{\leftmark}
\lohead{\rightmark}
\ohead{\pagemark}
\renewcommand\chaptermarkformat{}% no chapternumber in header
\setkomafont{pageheadfoot}{\normalfont}
\renewcommand*{\pagemark}{{\usekomafont{pagenumber}{\thepage}}}
% define new layers
\DeclareNewLayer[
background,
oddpage,
align=tr,
hoffset=\paperwidth,
voffset=0pt,%distance from top
width=1cm,% width of the swatch
height=\dimexpr\voffset+1in+\topmargin+\headheight\relax,% height of the swatch
contents={\textcolor{swatchcolor}{\rule{\layerwidth}{\layerheight}}}
]{swatch.odd}
\DeclareNewLayer[
clone=swatch.odd,
evenpage,
align=l,
hoffset=0pt
]{swatch.even}
\DeclareNewLayer[
foreground,
oddpage,
align=br,
hoffset=\paperwidth,
voffset=\paperheight,
width=3em,
height=2\baselineskip,
contents={{%
\setlength{\fboxsep}{0pt}%
\colorbox{white}{\parbox[c][\layerheight][c]{\layerwidth}{\centering\pagemark}}%
}}
]{pagenumberouterbottom.odd}
\DeclareNewLayer[
clone=pagenumberouterbottom.odd,
evenpage,
align=bl,
hoffset=0pt
]{pagenumberouterbottom.even}
\addtokomafont{pagenumber}{\color{black}\bfseries}
\AddLayersToPageStyle{scrheadings}{pagenumberouterbottom.odd,pagenumberouterbottom.even}
\AddLayersToPageStyle{plain}{pagenumberouterbottom.odd,pagenumberouterbottom.even}
% add layers to every pagestyle
\AddLayersToPageStyle{@everystyle@}{swatch.odd,swatch.even}
\newcommand\swatchcolor[1]{\colorlet{swatchcolor}{#1}}
\swatchcolor{white}
%Font
\usepackage{carlito}
\usepackage{fontspec}
\setmainfont{Carlito}
\begin{document}
\tableofcontents
\newpage
\vspace{-2in}
\chapter*{First chapter}\swatchcolor{red}
\Blindtext[1]
\newpage
\chapter{Second chapter}\swatchcolor{blue}
\Blindtext[1]
\chapter{Third chapter}\swatchcolor{green}
\Blindtext[1]
\end{document}
