I want to create a block with multiple channels to be 3D printed - I would perfer to model the channels as "pipe" and then invert the model to create the block with the channels.
This may make 3D printing a challenge for some if this requires interior supports that aren't able to be plucked out later. I use dissolvable support material in those cases.
Multi-body solid.
Combine - subtract.
Attach your *.sldprt file of what you have attempted so far.