There’s a pretty cool piece of interactive 3D media over here that is useful in visualizing the relationship between the physical organs in the abdomen:
I labeled the first screenshot below. By comparing the first and second screenshots, ￼you can see that both the spleen and pancreas are located mostly behind the stomach. Part of the spleen pokes out from the upper edge of the stomach and about half the pancreas pokes out from the lower edge of the stomach. The spleen and pancreas just about meet near the middle of the exterior of the stomach.￼
I also labeled the adrenal gland, which is sitting on top of the right kidney in the first image. The adrenal gland has often been regarded as a physical aspect of kidney yang.￼ The pancreas, which is also a gland, has a somewhat similar functional relationship to the physical spleen as the adrenal does to the kidney, in that the combination of the known physiological functions of the gland plus organ in each pair cover a range of activity that is fairly close to the traditional Chinese medical description of the Zang organs alone. I am definitely not the first person to remark about this. It has been discussed profusely in the Chinese medical journal literature in China itself. I just found the media on this webpage to be helpful in visualizing the relationships￼￼￼.