盛る: serving rice and heaping up soil
Compare serving freshly cooked rice into a bowl with heaping soil in a garden corner. Use the object, location, and resulting mound to read the two senses of 盛る.
Rice as the object and a bowl as its destination
「炊きたてのご飯を茶碗に盛る。」 means “I serve freshly cooked rice in a bowl.” Freshly cooked rice is what is served, and the bowl is where it is placed. ご飯を marks the object and 茶碗に marks its destination.
盛る here describes serving rice into the bowl. No number of bowls or quantity of rice is given, so the example does not become a comparison of container counts or portion sizes.
Heaped soil and the resulting mound
「庭の隅に土を高く盛って山を作った。」 means “I heaped up soil in a corner of the garden to make a hill.” Soil is what is heaped, and the garden corner is its location. 盛って links heaping the soil with making the resulting hill or mound.
With 土を高く盛る, the example uses the sense of heaping up soil. Its object differs from the rice being served; the example does not add loading a vehicle or exaggerating a story as further senses.
Follow the verb’s object and location
The rice example combines ご飯を with 茶碗に, while the garden example combines 土を with 庭の隅に. Those objects and locations distinguish serving food from heaping soil in the actual sentences.
The rice example uses the nonpast 盛る, while 盛って山を作った describes the past garden action and its result. Preserve each sentence’s timing as well as the object acted on.
What was heaped up in the garden example, and what was made as a result?
Show the answer and why
Soil was heaped in a corner of the garden to make a hill or mound. 盛って acts on 土, and 山を作った states the resulting formation. This is the soil-heaping sense rather than serving rice or counting bowls.