Not sure if this is well known, but Bone Prison (Ghastly modification, upgraded to cause vulnerability) generates corpses when used with Hewed Flesh.

You can test this out yourself by casting Bone Prison on some far away enemy; with 35% lucky hit chance from my items and a 12% corpse trigger from (3/3) Hewed Flesh, I generated ~3 corpses each time. This seems to replicate fairly well. Against two enemies, I got 6 corpses.

Random theory: My guess is that the vulnerability generation is coded as a zero damage-over-time ability which also has some internal lucky hit chance - maybe just the base level. That is, there is a 12% chance to make a corpse with Hewed Flesh. With my 35% lucky hit, that gives (12%)*(35%) = 4.2% chance total. Bone Prison has 6 "walls" that last 6 seconds, this means there 6*6*2=72 procs over the duration if there's 2 ticks per second. So 72 procs with a 4.2% of generating a corpse each time gives 3 corpses in expectation, exactly in line with the observed value. If you take the normal approximation to the binomial, the setup is {n = 72, mu = 72*4.2%, sigma = sqrt(4.2%*(1-4.2%)*72)} giving a 95% CI of [2.631 – 3.417] which is quite tight. So, the number of corpses generated will actually be quite consistent as well.

The tldr/takeaway from this is that Bone Prison will make about 3 corpses per enemy (given my stats), scaling directly with the enemy count. With 10 enemies, you would get 30 corpses assuming they live through the 6 second duration of the prison.

For a build like Infinimist, it might be useful to use a malignant heart to get permanent decrepify and then slot in bone prison for consistent corpse generation against bosses.

edit: I just realized you can also drop Reap if you are using Bone Prison.