For the chipotle potato salad: Put the potatoes in a large pot, cover with cold water and add a generous amount of salt. Bring to a boil and cook until a skewer inserted in a potato meets with no resistance, about 25 minutes. Drain and transfer to a baking sheet. Let cool for 5 minutes, then slice into 1/4-inch-thick slices.
While the potatoes are cooking, whisk together the mayo, vinegar, chipotle, mustard and 1/2 teaspoon pepper in a large bowl; add salt to taste. Add the potatoes, green onions and cilantro and mix gently to combine. Season with more salt and pepper, if needed.
For the corn relish: Heat some canola oil in a saute pan over high heat. Add the corn, season with salt and pepper and cook until heated through, about 2 minutes. Add the piquillo peppers and jalapeno and cook for a few minutes longer.
Transfer the corn mixture to a bowl, add the olive oil, green onions and lime zest and juice. Let sit at room temperature for at least 15 minutes to allow the flavors to meld.
For the basil oil: Prepare an ice bath. Bring a small pot of water to a boil over high heat.
Add the spinach to the boiling water and blanch for 20 seconds. Remove with tongs and plunge immediately into the ice bath. Let sit 5 minutes, then drain and squeeze out any excess water. Set aside.
Combine the oil and basil leaves in a blender, add salt and pepper to taste and blend for a few minutes until the basil is completely pureed. Add some of the spinach (to make it greener). Strain through a fine-mesh strainer set over a bowl.
For the striped bass: Preheat the oven to 250 degrees F.
Brush a cazuela or small cast-iron pan with canola oil. Season the bass on both sides with salt and pepper. Put the bass fillets in the pan and roast until opaque in the center, about 30 minutes.
Drizzle the fish with the basil oil and sprinkle with lemon zest. Serve with the potato salad and corn relish.