Add all ingredients to a medium saucepan and press as much of the fennel below the oil as possible (the oil will barely cover everything at first but it will cook down later). Bring to a simmer over medium heat, cover, and reduce to low to maintain a very low simmer. Cook for 1 hour, stirring occasionally, or until the flavor the oil has reached your liking. Remove from heat and strain through a fine mesh strainer set over a medium mixing bowl. Allow to cool to room temperature, transfer to an air-tight container and store in the refrigerator.
I tried a batch using only a few orange zest strips and didn't get a lot of orange flavor. The next batch I increased it to 6 strips and the orange flavor was pronounced. Hopefully that helps you decide how many to use.
I tried a batch using 1/2 teaspoon red pepper flakes and didn't get much of any heat. The next batch I increased it to 1 teaspoon and while not spicy, there is a little kick on the finish.
I haven't tried cooking the oil any longer than 1 hour as I assumed all of the fennel flavor has been extracted at that point. But I would love to know the results if you cook it longer!
Add oil and spices together in a small saucepan, cover and heat over medium-low until just starting to simmer, about 3-5 minutes. Remove from heat and allow spices to infuse the oil for at least an hour, longer if possible.
Layer the zucchini in a colander set over the sink, sprinkling lightly with salt as you go. Place a heavy object on the top to weigh it down (I used canning jars). Let stand for 1 hour, then pat the slices dry with paper towels or clean kitchen towels.
Combine the vinegar, water, and 2 tablespoons of salt in a large pot and bring to a boil over medium-high heat. Stir to dissolve the salt. Add the zucchini, using a wooden spoon to submerge it in the brine. Cover and boil until the zucchini slices have lost their bright green color, about 3 minutes. Remove the slices from the brine and lay them on clean kitchen towels to dry for 1 to 2 hours.
Layer the dry zucchini in a quart sized canning jar and pour Aleppo oil over the top. You should have just enough to cover the zucchini but if not, pour over additional oil. Screw the lids on tightly and let sit at room temperature for 24 hours. Check to make sure the zucchini remains completely covered; if not, add more oil.
Let the zucchini cure in the refrigerator for 1 week before using, then store in the refrigerator for up to 3 months. To serve, remove from the jar only as much as you plan to use and let it come to room temperature. Top off the jar as necessary to keep the zucchini submerged.
You can completely skip the first step and just use plain ol' olive oil. I just wanted to experiment and try something different.
Heat oil in a medium saucepan and over medium heat until shimmering. Add the garlic and anchovy paste and cook, stirring frequently, until fragrant, about 30 seconds. Add the remaining ingredients and bring to a boil. Cover, reduce heat to medium-low, and simmer for 30 minutes. Remove from heat and pour liquid through a fine mesh strainer set over a large bowl. Transfer to several small air-tight container (I use canning jars) and cool to room temperature. Transfer to the refrigerator if you plan to use within a few days; otherwise, store in the freezer for up to 6 months.
I call for anchovy paste only because that is what I had on hand. You can substitute a couple minced whole anchovies or leave them out all together if you prefer.