I bought this pack of chalkboard stickers from a craft shop last year and created a couple of designs for them on the Cricut. They're decent, but they're not sticky enough to go on curved surfaces (I wanted them for jar labels, doh). But they stick down flat nice enough.
I tested a liquid chalk pen on them with a damp bit of kitchen roll/paper towel and it came off alright. Also, you can cut them down if they're too big.
I thought I could offer them for Patreon rewards, since I'm taking so long with the Prowl print (I'm so sorry, I know I've been SO slow with him, I'm gonna try and finish him this month). I thought these would be an addition for when Prowl goes out to patrons.