IPA: /ˈsɒlɪdli/
KK: /ˈsɑlɪdli/
In a firm or strong way that shows stability or strength.
The building was constructed solidly to withstand strong winds.
Solidly → It is formed from "solid" (from Latin "solidus", meaning whole or firm) and "-ly" (meaning in a manner of). The word "solidly" means in a firm or stable manner.
Think of something being 'whole' or 'firm' ('solid') and how it is done 'in a manner' ('-ly'). This helps you remember that 'solidly' means to do something in a firm way.