I would like to make a DIY drop seeder like the one shown here. I am just very inexperienced with acrylic/plexiglass as a material.
A drill bit will cut holes in acrylic, but don’t use acrylic or you will probably experience breakage like your example. Use polycarbonate, a name brand is Lexan. It can be purchased in the same thickness. It is usually a bit more expensive but it will not crack even when dropped, or hit with a hammer but will preform exactly the same otherwise.
I don't see notches as much as through-holes. Acrylic is easily cut to specifications by using a CO2 laser. For the design in the video, one could get away with 3 mm thick acrylic, keeping the weight down while providing enough strength for such a device.
Ed suggests polycarbonate, which is stronger and cannot be cut with a laser.
Finding a local makerspace, or posting a query on a laser forum such as Lightburn Software should find you a willing cutting resource. I've done a number of custom laser projects for members of both our local makerspace and visitors to the above noted forum.
Using a service is also a possibility, but the costs increase substantially for established industrial services one would find.
