What is the proper laboratory technique to place a solid in a beaker that will be weighed?
There is no correct or universal weighing protocol per se. The key question is what is the desired level of accuracy? Your teacher's approach is quite cautious but this is not the universal way, as what you did is also common. He/she is apparently avoiding a spatula as well. I personally dislike paper and plastic weighing boats. If you ever had a chance to weigh dry salts or organic crystals on a dry day, these materials charge like crazy and literally all particles fly apart the moment you touch the plastic boat with gloves.

Pharma companies, where a high level of accuracy is required and legal formalities are important, chemists often use weighing funnels. They are not popular in academia (pricey!). In the picture, you see a latest type of balance which avoids static issues. On the top you see a weighing funnel. This one is plastic coated with anti-static material but glass is more common. After weighing, the funnel containing the weighed substance is placed on the mouth of a volumetric flask and washed very carefully. You can't do this with paper.


https://www.laboratorynetwork.com/doc/new-smartprep-weighing-funnel-weigh-in-samples-more-accurately-0001