Secret Weapon Miniatures have released their Wetlands Scenic Kit basing set.
From their website:
I am happy to announce that the “Instant Scenery Kit: Wetlands” is now available to purchase!
This kit includes everything you’ll need to add grass, underbrush moss and water to your Blasted Wetlands bases — but also includes fine sand for those of you wanting to make a batch from scratch.
The two bases shown in the product photo are also the subject of a video I’m finalizing that will demonstrate the products in this kit so you can see a step-by-step demonstration of the kit in action.