Hook: Floor Medium (Blue Square)The Potted Tree: Dead Ziost Tree decoration fits into a blue medium square floor hook.
How to Get a Potted Tree: Dead Ziost Tree Decoration
Cartel Pack Decorations
The Potted Tree: Dead Ziost Tree decoration can be dropped from Oppressor Alliance Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Oppressor Alliance Pack, include a random selection of items from the Oppressor Alliance collection of items. You aren't guaranteed to get a Potted Tree: Dead Ziost Tree decoration from a Oppressor Alliance Pack, but it is one of the few ways to get a Potted Tree: Dead Ziost Tree deco apart from buying it on the GTN from another player.
If you're looking to get a Potted Tree: Dead Ziost Tree, the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. If it's very rare and not available on the Cartel Market, you could try buying from the GTN and hope you get it.