Learn Finnish: Savesta tehty maljakko on todella painava. - The vase made of clay is really heavy.

This is the core rule of complex participial attributes in Finnish. When a participle like tehty (made) describes a noun (maljakko) and has its own modifiers (like savesta - out of clay), those modifiers must be sandwiched directly before the participle. It literally translates as "the out-of-clay made vase". You cannot put the modifier after the noun like you would in English.

Why is the word for clay (savi) in the elative case (savesta)?

In Finnish, when you express what material an object is made out of, you use the elative case (-sta / -stä). It literally means "out of clay" or "from clay".

What verb form is tehty here?

It is the passive past participle (often called the TU-participle) of the verb tehdä (to make). It is used here as an adjective to mean "made". It is passive because the vase didn't make itself; it was made by someone.

Is painava (heavy) related to the verb painaa (to weigh)?

Yes! Painava is technically the active present participle (the VA-participle) of the verb painaa. It literally means "weighing", but in everyday Finnish it is simply used as the standard adjective for "heavy".