I usually try to build flows now that don’t ask for coupon codes at checkout (because that leads to deal searching right at the last moment). I prefer dedicated URLs with embedded offers as much as possible.

If you need to go the coupon code route, I recommend how Namecheap does it: they registered a unique domain (namecheapcoupons.com) that publicly list all coupon codes. They rank #1 in organic search results.

But, as a general rule, I encourage you to avoid working with deal sites and coupon affiliates. This is a general rule, but they tend to drive very little incremental revenue. You should also disallow any PPC campaigns using your branded terms.