This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of thick? Also thick.
The reading is the same as what you learned with the kanji. No thick books needed to understand this reading, yeah?
I wonder how a hole was made in this thick fence.
When I visited the Tofugu office, I received a very warm welcome.
Koichi found a sick earthworm resting on some thick moss.