With Auction Pro Master, you have to add items to an item group.

In game:
/APM Config

Type in a name for a new list.
Check every box, so the category goes by the configuration you're about to do.
Rather then the defaults, listed elsewhere.

Go to the Add tab, and add any item (in inventory).
A given item can only be added to one group at a time.
If you want to have the item in another group, you'd have to remove it from an existing group first.
Off the bat, items won't be in any group.

Undercut value should be set to 1 copper.
I set bids to be 100% of the buyout.

You have a fall-back value, and should check to use that value.
This should be near the upper range you think the item will sell for.
Also set a minimum value for your gem/glyph.
If it goes below the minimum value, then it will be posted at the fallback.

Each of the sliders, that control stack size and evaluating prices, should be set to singles.

The other values (slider bars, towards the bottom) which control pricing, I set to 100%.
So it won't go above my maximum price, or undercut more then 1 copper.