Trying a bit with proxi printing it seems like the best way of generating playable proxies, is to cut the proxie to exactly match the inner card frame and glue it to an original (keeping its black border).
This script helps you to create a proxie sheet with 9 cards, cropped to the right size and aligned, so that one cut between adjacent cards is enough.
Simply collect the links of the 9 proxies you need from scryfall and past them line by line into the cards.txt
cat cards.txt via v3.10.4
https://scryfall.com/card/mh2/439/scalding-tarn
https://scryfall.com/card/mh2/439/scalding-tarn
https://scryfall.com/card/mh2/439/scalding-tarn
https://scryfall.com/card/mh2/440/verdant-catacombs
https://scryfall.com/card/mh2/440/verdant-catacombs
https://scryfall.com/card/mh2/440/verdant-catacombs
https://scryfall.com/card/mh2/437/marsh-flats
https://scryfall.com/card/mh2/437/marsh-flats
https://scryfall.com/card/mh2/437/marsh-flats
then run the script, which will create proxi_set.pdf
python build_proxi.py