Special equipment: 8-inch round metal cake pan (preferably 2 to 3 inches deep)
Preheat the oven to 350 degrees F.
Pour 3/4 cups of sugar into round metal flan mold. Place over medium heat and carefully move the pan frequently, without stirring, until it takes on an amber hue. Off heat, swirl the caramel so that the bottom and sides are lightly covered. The caramel will be very hot. Set aside to cool.
Add the remaining 1/2 cup of sugar, almond milk, orange juice, sliced almonds, egg yolks, eggs, vanilla, salt, and zest to a blender and mix on lowest setting until blended.
Carefully pour the custard into prepared mold and cover tightly with aluminum foil. Place the prepared mold in a larger roasting pan. Pour enough hot water into the pan so that it comes halfway up the sides of the mold. Place the pan in the oven and bake for 60 to 75 minutes until a knife inserted into the center comes out clean though it may still appear wobbly.
Allow to cool completely inside the water bath then refrigerate covered at least 4 hours or overnight.
To un-mold the flan, run a thin knife along the side of mold. Gently shake to loosen. Invert a large plate over the flan and quickly invert the mold in one motion. The flan will gently drop onto the plate and the caramel will flow out so allow extra space around the flan.
The caramel can also be done in a small saucepan, then poured into the mold.