What is a physical manifestation
Physical manifestation is purpotedly an event when a spirit attains a physical form during which it can freely communicate and interact with the Magician or anyone around.
We split the physical manifestation into two categories: full manifestation and partial manifestation.
Full manifestation is when the spirit is fully materialized, its whole body is visible and the manifestation is consistent (stable). Partial manifestation can be arms, legs, head, shoulders, usually also flowing from one body part to the other one during the course of the evocation.
Concerns regarding physical manifestation
I am not a big fan of the idea of spirit being "materialized", I would rather explain it as "Astral light being densified to the point of being visible" than "assemling particles to the form of a spirit". It's true that I was able to achieve only a partial manifestation, never a full one, but I doubt the process is any different. What I believe is really happening during the manifestation is the Magician getting to the right trance state of seeing the spirit as real as it was truly physical.
There also is a claim that anyone will be able to see such a manifested spirit, not only clairvoyant mediums. Well, I worked with people before and they really did see what I saw, but was it because the spirit was truly physically materialized or was it because they were part of the evocation from the beginning to the end and the ritual itself had the same effect on me as it had on them? Would they see the same what I saw if they came in after the manifestation occured? I personally doubt that.
How to for physical manifestation
The setup is as always, just in the beginning you state your request for the spirit to manifest its presence in a visible form. Shadow evocation technique we learned before has amazing results regarding physical manifestation, and it can also help you to pinpoint the exact location of the manifested spirit (in the middle of distance between you and your shadow on the wall).
Main problem regarding physical manifestation is time. You must be sure you are able to spend about two hours performing the ritual, calling the spirit to manifest again and again, cursing it and commanding it by all godly and godless names you can think of and doing so till the spirit appears. I know you were expecting a bit more, but this is really no-brainer, it's just time consuming.