Hello, I recently acquired a lovely twin trunk american larch tree which I will begin styling work on in the coming year, in the meantime I am looking to find a slab on which to plant the tree, I have looked several places online and have found very limited options. I would like to have this new pot for it by early spring of 2022, and I am seeking advice as to where to purchase a suitable slab, so i'm wondering where best to find a good slab.

PS. Sorry to ask this in this section of the forum, if there is a better section where I should ask this question please let me know.