Substitute the minor revision number of the latest Linux 4.19 kernel for every "XX" below.

Please note that I've disabled UEFI in the BIOS since I don't use it.

1] In my Slackware64 14.2, the only disk sets I do not install are E, F, KDEI, T, and Y.
2] Update Slackware64 14.2 first.

su - # Or login as root.
cd /etc/slackpkg
cp -p mirrors mirrors.orig
vi mirrors # Enable a mirror.
slackpkg update
slackpkg upgrade-all
shutdown -r now

3] Do the following to compile the latest Linux 4.19 kernel:

su - # Or login as root.
wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.19.XX.tar.xz
wget http://ftp.slackware.com/pub/slackware/slackware64-current/kernels/huge.s/config
cd /usr/src
tar xJpf ~/linux-4.19.XX.tar.xz
rm linux
ln -s /usr/src/linux-4.19.XX linux
cd linux
make mrproper
mv ~/config .config
make oldconfig # When asked for input, use the default or the option you think is best.
make menuconfig # You may skip this. Do this only if you need to make configuration changes.
make bzImage
make modules
make modules_install
cp arch/x86/boot/bzImage /boot/vmlinuz-huge-4.19.XX
cp System.map /boot/System.map-huge-4.19.XX
cp .config /boot/config-huge-4.19.XX
cd /boot
rm System.map
ln -s System.map-huge-4.19.XX System.map
rm config
ln -s config-huge-4.19.XX config
rm vmlinuz
ln -s vmlinuz-huge-4.19.XX vmlinuz
/sbin/lilo

4] Congratulations. Your Linux 4.19 kernel should now work after a reboot.