I just read something on this the other day. I will try to find the site and post it. It was actually pretty easy looking. They just used diff shades of brown and brushed it on. I don't know if that's what the creator of the link you posted did but it's worth a shot.
It looks dry brushed to me. Start with tan colored fondant, brush some dark brown ( I'd use gel color and vodka) and wipe most of it off. If you want texture you'd need a wood grain mat.
I made a wood floor look on the base of a basketball cake I did...I just made grooves in the fondant like the planks on a wood floor with a fondant tool and painted a base coat of light brown and then when dry painted the darker brown over it...like you're staining a floor. The color goes into the grooves and the brushing gives it the wood look.
I've made a few signs like that. I just used a pizza cutter to gently score some random lines then dry-brushed some brown gel color on it. I started with a light brown piece of fondant or gumpaste. Here's some that I did:
Thanks so much for your replies. Debbie, your plaques look great!