Pen turners will make pen blanks from small pieces of wood perhaps some shavings.
You should search this forum for casting pen blanks. It is very important to remove air pockets. This is done with a pressure pot and either high pressure or vacuum depending on your equipment.
I think the folks who cast use an acryllic resin which is easy to turn.
I would not use wood glue. It will shrink too much, which will cause cracking and it is very brittle and tough on the turning tools.
You will need a lot of volume of resin. Likely going to spend more for resin than a solid wood bowl blank.