Hi Tessa,
Yes, theoretically you could use EasyCast to do this project, but I wouldn’t for a couple of reasons:
1.  Even when fully cured, it is still relatively soft.
2.  It mixes thick, so bubbles are going to be difficult to get out, especially since this sounds like this is a deep pour.
Have you looked at the larger kits of super clear resin?  They are more affordable per ounce:
https://shop.resinobsession.com/collections/resin/products/resin-obsession-super-clear-resin-12-oz-kit