Arun Prakash Jana has already described how to install SliTaz in frugal mode on an UEFI computer. But he did install the kernel and the rootfs in the ESP partition.
IMHO, the ESP partition should be reserved for boot loaders and no operating system or software should be installed in it. This document explains how to do a frugal install of SliTaz Next (32bit) on the Windows partition, C:

• Start Windows and open the file manager.

• Select (C:) and create a new directory at root; say slitaz.

• Open slitaz and create a directory, say next in it.

• Plug your EFI LiveUSB and copy the files bzImage and rootfs.gz from the \boot directory of the Live into the \slitaz\next directory of (C:).

• Copy the boot loader - bootia32.efi for a 32bit EFI system (or bootx64.efi for a 64bit EFI system) - from the \efi\boot directory of the Live into the \slitaz\next directory of (C:).

The boot loader must be installed in (ESP); this partition is not mounted at boot and is hidden.
Mount (ESP) : from Windows 8/10, right-click on the Home button in the bottom left corner of the screen. In the context menu that opens, select Windows PowerShell (admin). The User Account Control will warn you that Windows PowerShell wants to modify the system; confirm by clicking [ YES ].

mountvol s: /s

You can check (ESP) is correctly mounted listing the directories and files it contains:

dir s:

Create a directory, say slitaz, in the EFI directory of (ESP)

mkdir s:\efi\slitaz

Copy the boot loader into it.

• For a 32bit EFI computer, type:

move \slitaz\next\bootia32.efi s:\efi\slitaz\grubia32.efi

• For a 64bit EFI computer, type:

move \slitaz\next\bootx64.efi s:\efi\slitaz\grubx64.efi

Note we have renamed the file; this is not a necessity but it'll help to you remind that SliTaz is launched with GRUB 2.

Create a \boot\grub directory in (ESP)

mkdir s:\boot\grub

Create the configuration file:

notepad s:\boot\grub\grub.cfg

-Example-

### CONFIGURATION FILE FOR GRUB 2 ###
#

# Comment the line if you want SliTaz to start immediately or
# change the value to define the time (seconds) to wait before booting.
set TIMEOUT=-1

# Menu 0: SliTaz Next (ISO 20170930 - kernel 4.9.30)
menuentry "SliTaz Next - frugal install" {
   set root=(hd0,3)
   linux /slitaz/next/bzImage ro root=/dev/null video=-32 autologin
   initrd /slitaz/next/rootfs.gz
}

This config file considers (C:) is (hd0,3): the third partition of the first hard disk, this is generally the case. To verify what the main partition of Windows is, run the Diskpart utility; ask for the list of the disks, select the Windows disk and list its partitions:



Unmount (ESP):

mountvol s: /d

You don't have anything else to do than to disable the Secure Boot. You've already did it when you created your EFI LIveUSB.
If you came directly to this tutorial without doing an EFI LiveUSB, see step 5 of HOWTO do a SliTaz LiveUSB for EFI computers.

Reboot the computer and access the Multiboot mode. On the hp Laptop 17-bs032, press the [F9] key immediately after you've powered on the computer until the Boot Manager displays the list of the disks where it found a bootx64.efi file in a \EFI\BOOT of a FAT32 partition:



Select Boot From EFI File. The EFI File Explorer displays the list of the volumes found; select your hard disk then EFI > slitaz > grubx64.efi to run GRUB 2.

 
# Menu 1: boot Slitaz from ISO file
menuentry "SliTaz - LiveISO" {
   loopback taziso (hd0,3)/slitaz/slitaz.iso
   linux (taziso)/boot/bzImage ro root=/dev/null video=-32 autologin
   initrd (taziso)/boot/rootfs.gz
}