Puppy can run in different pupmodes.
This controls how the save is written to, as Puppy is run.
There are several pupmodes, but these two are the common used, after installing Puppy to a drive. (USB, sdcard, emmc, HDD)
pupmode 12
The save is mounted read/write.
Writes are done at the time the need happens.
Writes automatically.
No control by you.
pupmode 13
The save is mounted read/write with limits on writes.
A set time period.
Click on desktop save icon.
At shutdown.
Pupmode 13 turns on all select-able save options, offered in Puppy Event Manager->Save Session.
Not knowing what exact boot loader you are using.
In general look for the config file that is providing the boot menu entries.
menu.lst
Syslinux.cfg
grub.cfg
Open the file in a text editor.
Find the entry you use to boot with.
Look for pmedia=atahd or anything pmedia=
Change this to pmedia=usbflash
Save and reboot using this menu entry to boot.
That should make Puppy run in pupmode 13
Should now have save icon on desktop.
Save session options select-able in Puppy Event Manager->Save Session
How Puppy works:
http://bkhome.org/archive/puppylinux/de ... works.html
This will tell you all about pupmodes.
Note:
This how puppy works info has not been updated for using a save folder.
But it works the same as a save file, depending on the pupmode.