Learn Turkish: Astarı karıştırma kasesinde spatula ile karıştır. - Mix the primer in the mixing bowl with the spatula.

It uses a verbal noun purpose compound. karıştırma is the short verbal noun for mixing. To link it to kase (bowl) to form the concept of a mixing bowl, Turkish adds the possessive suffix -si. Finally, the buffer letter -n- and the locative suffix -de (in) are attached to the end.

Why does the sentence use astarı instead of just astar?

The suffix -ı is the definite accusative case marker. It shows that astar (primer) is the specific direct object of the verb. You are not just mixing any primer in general, but rather the specific primer prepared for this task.

The words karıştırma and karıştır both appear here. How is this verb root constructed?

They both originate from the root karışmak (to get mixed up or blended). The -tır suffix is the causative marker, turning the verb into karıştırmak (to cause to mix, meaning to stir or mix something). In this sentence, karıştırma is the verbal noun and karıştır is the second-person singular imperative command.

Could I change the word order to Astarı spatula ile karıştırma kasesinde karıştır?