"firmly assembled" is correct and usable in written English.
You can use it when you want to indicate that something has been put together very carefully and securely. For example, "The parts of the machine were firmly assembled in order to minimize any potential risks."
Accordingly, rods and blocks of polished steel are firmly assembled, yet the scenarios they describe appear to embody his unresolved cultural insecurities.
Serving to exclude the possibility of contamination, we found that the sequences of both genes were firmly assembled into chromosomes 12 and 7, respectively (data not shown), and not randomly annotated in an unplaced contig/scaffold.
Gently press the top layer down onto the creme so the assembled cake is firmly pressed against the acetate all round.
I assembled a team that are all firmly marketing execs who have a solid love of the industry, as well as experience in conventions like Comic-Con International in San Diego and New York Comic Con.
As the assembled hacks dashed for the doors, hands were firmly in pockets; Sony Pictures hasn't denied suggestions that the clapping came not from journalists but the cinema's own sound system.
"I believe I have assembled an excellent bunch of players, and I still firmly believe that over time they will prove their worth and push this club to the next level," said Hutchings.
The entire setup was assembled on an optical breadboard with all components being firmly fixed to avoid vibrations.
The Los Angeles County district attorney, Gil Garcetti, has assembled an impressive task force and says he has the investigation firmly in hand.
"We have assembled a team that has successfully launched novel products before, and we firmly believe in the chances of success for this product," he said.
The Democratic convention was based here in the state capital, but the attention of the 11,500 Democrats who assembled in the Pepsi Arena, among them the president of the United States, was firmly focused on New York's City Hall.
Robert Gottlieb is a firmly even-handed biographer and his engagingly zippy account focuses particularly on exposing the cracks in the contradictory stories that Bernhardt and her hagiographers assembled about her life.
