twm (Tab Window Manager) is the standard window manager for the X Window System since version X11R4.

Prerequisites

Install Alpine Linux
Create a user account (optional but recommended)
Enable the Community repository
Install Xorg

Installation

In home directory create a file named ".xinitrc":

vi ~/.xinitrc

Or, if you prefer nano text editor

nano ~/.xinitrc

Write to file:

Contents of ~/.xinitrc

exec twm

Save the file.

Install twm

# apk add twm

If doing no further configuration, you will also need xterm to open apps:

# apk add xterm

Start the X window manager

startx

You will be greeted with a black screen. Hold left mouse button and select "XTerm". Type in a program name to launch it.

Keyboard layout

The keyboard layout defaults to US qwerty. If you use an alternative layout (e.g. Colemak) you can install setxkbmap:

# apk add setxkbmap

Then switch to another layout (example for colemak):

setxkbmap us -variant colemak

Customizing twm

twm can be extensively modified. The default system-wide default configuration file for twm is /usr/share/X11/twm/system.twmrc and the per-user configuration is ~/.twmrc. The user file completely overrides the system, so it's recommended to start modifications by copying the system-wide file to the per-user file.
Some very basic customizations which many users do are below:

Add basic alt+tab support

The following can be added to the config enable basic alt+tab support for rapidly switching windows to the front:

"Tab" = m : root|window|frame|title : f.circleup

Add maximize, and close buttons

First install some bitmaps for the buttons:

# apk add xbitmaps

Then edit the config file and add the following:

Function "maximize" { f.fullzoom f.focus f.nop }
RightTitleButton "icon"=f.function "maximize"
RightTitleButton "xlogo11"=f.delete