Good question. Apology for the delay in answering your question.
Jala neti is very easy practice subject to fulfillment of certain precautions. Most people are pleasantly surprised after even their first attempt, at just how simple and effective this method of health maintenance is. Once learned, this jala neti practice can be done in a couple of minutes, and like daily routine of body cleansing - showering and cleaning the teeth.
https://www.webmd.com/allergies/ss/slideshow-nasal-irrigation
In simple jalneti, the water simply flows up one nostril to just above the bridge of the nose where the usual air flows meet, backwards into the middle cavity and then the water flows down and out the other side of the nose. As you can see in the above figure that, in this route, it passes by the frontal and mid nasal sinuses. There should be no flow of water back towards the throat or into the mouth. When done correctly, there is usually very little sensation as the water will be the same temperature as the blood, and the salinity will be the same salinity as the blood.
So, as you asked about the angle of body. Jalneti can be done sitting as well as standing. In standing posture, there should be around 45 degree from the pelvic region (waist) keeping neck in the same alignment. Now, horizontally, the neck should turn around 45-60 degree to the respective side of the nostril through which the water has to be poured by inserting nozzle of the neti pot, such that the water should pass-out from the other side of the nostril. The position of the hand holding the neti pot is also equally important as illustrated in the below figures. All the three positions are to be considered for smooth flow of water from one nostril to another. However, there is no need to stick to this hard and fast position, as every body has his/her own alignment and anatomical structures that discriminate these positions from other ones. You can adjust all these positions suitable to your needs and that allow free flow of water. Also ensure that the mouth is open throughout the process of flow of water from one nostril to the other nostril. However, it would be advisable to practice jala neti first time, under the guidance of qualified yoga therapist.
I hope I have answered your question to your satisfaction. If still there is any doubt, please feel free to ask further.
