How to prepare and process to installation is indicated here:
https://slint.fr/doc/HandBook.html#_install_slint

For the impatient: write the ISO on a DVD or an USB stick, insert it or plug it in a computer, reboot.

Requirements:
Architecture: x86_64
Booting mode: BIOS or UEFI (preferred if available)
No Secure Boot enabled.
Slint can be installed on any drive, including USB sticks, with at least 50GB free.

The installation program, in text mode, is fully accessible to the blind using a screen reader or a
Braille display, proceeds by questions and answers with an integrated help and documentation.
Two partitioning modes are available:

Automatic: The media will be wiped out and dedicated to Slint, the main file system will be btrfs.

Manual: the user prepares a partition of type Linux, size at least 50G which will be wiped out and
chooses the file system (btrfs, ext4 or xfs). The media can be shared with other systems.

The btrfs file system is configured with subvolumes instead of separate partitions, with compression
dividing by 2 the space occupied on the media, ability to take snapshots and is well adapted to
SSD, NVMe and USB sticks.