Make the cashew ricotta, by placing the cashews in a food processor with all ingredients except the parsley. Process for a couple of minutes until fairly smooth. Mix in the parsley and pulse until it's mixed into the rest of the ricotta. Set aside.
Keep a pan of warm water handy to soak the noodles just before you layer them.
Mix your marinara with the meatless meat or lentils. It might be easier to do this if you heat the marinara a bit, and you can just do this in the IP. Set the IP to the saute function. Place the liner inside, add the marinara, the meatless meat or lentils and the oregano, and mix well and let it all come to a boil. You can also do this on the stovetop. Make sure your marinara is seasoned to your liking and add some salt and pepper if you need to.
As soon as the sauce comes to a boil turn off the saute function. Remove most of the sauce from the liner using a ladle, leaving just about ¼ cup inside. Add the cup of vegetable stock (or water) to the sauce that remains inside.
Soak the lasagna noodles in the pan of warm water for a minute. Layer on four noodles into the bottom of the pan by placing two noodles side by side and two more on top, crisscrossing them. Since your IP liner is round and your noodles are rectangular, you are not going to get a perfect fit, but that's fine. The space on the sides is going to let the sauce bubble up and cook everything nicely.
Layer on one-fourth of the meat sauce over the lasagna noodles.
Layer on one-fourth of the cashew parmesan.
Layer on one-fourth of the vegan ricotta.
Layer on one-fourth of the vegan mozzarella.
Repeat until you have built up three layers of the meat sauce and the cheeses. Over the fourth and final layer, layer the remaining meat sauce and parm and ricotta. Don't add the remaining mozzarella shreds.
Cover the Instant Pot with the lid, then set to the manual pressure cooking function for 12 minutes.
Let the pressure release naturally or force-release it 10 minutes after the end of cooking. Sprinkle on the remaining mozzarella and cover the lid and let it stand for another 10 minutes.
The longer you let it stand, the more the lasagna sauce will thicken up, so I recommend leaving it alone for at least 15-20 more minutes. But if you simply can't wait, cut it, scoop it out and dig in!