Consider the following MWE
\documentclass{beamer}
\usepackage{tikz}
\usepackage{tikz-3dplot}
\usetikzlibrary{positioning}% To get more advances positioning options
\usetikzlibrary{arrows}% To get more arrow heads
\usetikzlibrary{math,calc}
\usetikzlibrary{arrows.meta, bending, decorations.markings, angles, quotes, fit}
\usetikzlibrary{tikzmark}
\usetikzlibrary{scopes}
\mode<presentation> {
\usetheme{Boadilla}
\setbeamertemplate{footline}{}% get rid of footer completely
}
\usepackage{booktabs} % Allows the use of \toprule, \midrule and \bottomrule in tables
\usepackage{amssymb, mathtools, amsfonts}
\definecolor{MyColor1}{rgb}{0.24, 0.59, 0.32}
\definecolor{MyColor2}{rgb}{0.85, 0.49, 0.19}
\definecolor{MyColor3}{rgb}{0.22, 0.42, 0.69}
\usepackage{tikz}
\usefonttheme{serif}
\begin{document}
\begin{frame}\frametitle{Examples}
\begin{center}
\begin{tabular}{c|c}
\onslide<1->{
$\langle\alpha,\beta\rangle = \langle\beta,\alpha\rangle =-1$
& $3\langle\alpha,\beta\rangle= \langle\beta,\alpha\rangle=-3$\\\midrule
& \\
\begin{tikzpicture}[scale=0.7, every node/.style={transform shape}]
\draw (-2,-2) rectangle (2,2);
\node (alpha) at (1.2,0) {$\alpha$};
\node (beta) at (120:1.2) {$\beta$};
\draw[->] (0,0) -- (0:1);
\draw[->] (0,0) -- (120:1);
\only<1>{
\foreach \angle in {60,180,240,300}{
\draw[->] (0,0) -- (\angle:1);
}
}
\draw[MyColor1] (0.5,0) arc (0:120:0.5);
\draw[fill=MyColor1, opacity=0.3] (0,0) -- (0.5,0) arc (0:120:0.5) -- cycle;
\end{tikzpicture} &
\begin{tikzpicture}[scale=0.7, every node/.style={transform shape}]
\draw (-2,-2) rectangle (2,2);
\node (alpha) at (1.2,0) {$\alpha$};
\node (beta) at (150:1.9) {$\beta$};
\draw[->] (0,0) -- (150:1.7320);
\draw[->] (0,0) -- (0:1);
\only<1>{
\foreach \angle in {30,60,90,120,180,210,240,270,300,330}{
\pgfmathsetmacro{\bigradius}{sqrt(3)}
\ifthenelse{\angle=30 \OR
\angle=90 \OR
\angle=150 \OR
\angle=210 \OR
\angle=270 \OR
\angle=330}{
\draw[->] (0,0) -- (\angle:\bigradius);
}{
\draw[->] (0,0) -- (\angle:1);
};
}
}
\draw[MyColor1] (0.5,0) arc (0:150:0.5);
\draw[fill=MyColor1, opacity=0.3] (0,0) -- (0.5,0) arc (0:150:0.5) -- cycle;
\end{tikzpicture}\\
& \\}
\only<2->{
\only<3>{
$\begin{pmatrix*}[r] \hphantom{-2} & \hphantom{-1}\\
\hphantom{-1} & \hphantom{-2}
\end{pmatrix*}$}
\only<4->{
$\begin{pmatrix*}
\only<4->{-2} & \only<5->{\color<5->{MyColor1}{-1}}\\
\only<5->{\color<5->{MyColor1}{-1}} & \only<4->{-2}
\end{pmatrix*}$}
&
\only<3>{
$\begin{pmatrix} \hphantom{-2} & \hphantom{-1}\\
\hphantom{-1} & \hphantom{-2}
\end{pmatrix}$}
\only<4->{
$\begin{pmatrix*}[r] \only<4->{-2} & \only<5->{\color<5->{MyColor1}{-1}}\\
\only<5->{\color<5->{MyColor1}{-3}} & \only<3->{-2}
\end{pmatrix*}$}
}
\end{tabular}
\end{center}
\end{frame}
\end{document}
It shows what it should at the the right position, i.e. the order of things that gets revealed is correct.. The only problem I have with the output is that the borders of the table (the central line and the first row) shift when some elements get revealed. I managed to get the two tikzpictures to stay in place, but when I add the matrices to the table they also start shifting...
I don't really understand where the problem is, since I think I applied the same technique to keep things in place in the entire frame, but it seems to sometimes not work (this is what I took as guidline)... I'm probably approaching this problem in the wrong way, but I don't really know how to keep things in place other than adding empty space where necessary.
Any hints on how I can get the entire table to stay fixed while revealing the different parts is appreciated.

\begin{frame}to\begin{frame}[t]helps. – Apr 24 '20 at 20:22\begin{overlayarea}{\textwidth}{0.5\paperheight} <content> \end{overlayarea}. Regarding the horizontal shifting you should write\only<overlay->{% (newline) <content of \only> }% (newline)otherwise a blank space is inserted after each\only{ }– BambOo Apr 24 '20 at 20:27pmatrix*but had somehphantoms. I replaced thehphantomwithpmatrix*but forgot to remove the minus.. Then postet the question and you were answered before I noticed.. And after that I felt like I shouldn' t modify the question anymore – Sito Apr 25 '20 at 07:15