I would say this is a model issue. How about separating the model in 2 parts: the flat bottom part with the legs, and the ‘envelope’ part that stands upright. Both parts can then be printed flat fairly easy. You’ll only need to think of a way to join the two again after printing, perhaps by modeling two holes in the stand part, and adding two pins on the upright part
Dutch books (for children) use the ‘AVI’ system to indicate the reading level. The system is structured: the higher the level, the more difficult the vocabulary in the book. The levels are:
For comparison, this is what Avi start looks like, the left page is written on average e5 level.
I don’t know if you are located in the Netherlands, if so, the libraries have dedicated sections for each of the Avi-levels, the librarians can show you where to find them. Also online you can find many lists of recommended books for each Avi level. Once you are comfortable with one level, move up to the next level until you have reached the end. By the time you are comfortable with e7 or plus, you can safely grab any other book you can find!
I always use union-groups when working with holes. Sometimes I even have to go through multiple nested union groups to get the desired result. But it always works when exporting, and you directly see the resulting shape in the editor (and the export).
I don’t run Linux , but I love Prusaslicer and it is available for Linux: https://flathub.org/apps/com.prusa3d.PrusaSlicer
In fact, in the EU that is regulated by article 6A (see https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A52021XC1229(06) ) . That states amongst other things that:
So maybe it wouldn’t apply for a 3 month period, but it does prevent stores from increasing the price by say 20% overnight and then give a “10% discount” the next day.