The key to octopus is a wine cork. No scientific reason but it works. I got a 3 lb. octopus covered it in water in a pot added a sliced shallot, some olive oil, 2 bay leaves and of course the wine cork. Brought that to a boil, then simmered for about 35 minutes or until a knife can easily slice through it. Once the octopus is done, drain this and rinse with cold water. At this point, I cut it into 8 pieces and put in the refrigerator for later.
When I was ready, I took the octopus out and coated it in a marinade. 1/2 cup olive oil, a whole lemon squeezed and also the rind grated, a handful of chopped fresh oregano and a pinch of hot red pepper flakes. I let that sit for about 30 minutes, no more. Then I grilled the octopus on the grill. About 5 minutes per side or just until it is crispy. Remember, the octopus has already been cooked so you are just warming it up and making it crisp.
I also took a head of celery and two heads of fennel sliced and sauteed that in olive oil and kosher salt. I served that underneath the octopus, which I cut up after it was grilled. Then I poured the marinade over the octopus before serving.
We had it at room temperature because I made it about 1/2 an hour before our friends got there. Truth be told, it is better warm.