Place the 10 pieces so they make a pyramid.
It is not as easy as you may think.
Print 1 base plate and 10 of the pieces. To make it possible to print them without support or rim, the balls are not made completely spherical, but they have a small cylindrical base.
My print: I have used standard black PLA (RFPLCXEU01B) in my DaVinci Jr. for the base plate. Quality was set to “Good”. It took app. 1h 30 min to print and it used 7.5 m filament (22.5 g)
For the 10 pieces I used Neo Green PLA (RFPLCXEU0AD). Two were made with “Good” (app. 30 min). Two were made with “Excellent” (app. 1 h 15 min). The last six were made with “Excellent” where the infill was reduced from 30% to 10% (app 1 h), those used 1.9 m (5.7 g). I got the best result by printing them one at the time.
SPOILER: I will not tell you what the solution is, but I will give you information, so you properly can find the solution fast. The pieces have to be placed symmetrically. The solution is with 4 layers, first a 4 by 4, then a 3 by 3, then 2 by 2, and on top just one ball. No ball is placed directly on top on another ball. The balls of the next layer are placed in the gap between the balls in the lower layer. Each piece can cover 1, 2, or 3 layers. If you describe the pieces on how many layers they cover, the solution can be described as 1111233112. The difficult part is 233. That is one across and two standing on each side.