What goes into the Press
The current official machine page names Burnt Residue as the input. The output per successful input is 1 Gold and 1 Seed, with the processed materials falling through the Press.
The drop-height rule
Burnt Residue needs a fall of at least 25 blocks. Build the vertical path first and keep the landing area clear; the exact construction footprint and launcher placement are design choices, not fixed values confirmed by the source.
Why it clogs
A drop that is too low, the wrong material entering, or excessive clustered input can leave material sitting on top. The collected troubleshooting discussions support using upstream filtering and a clear output path; exact fixes should be checked against the current build.