Стека лежит рядом с глиной.

Стeка is nominative singular, because it is the subject of the sentence — the thing that is doing the “lying.”

A native English speaker might expect something like стекa just to be a dictionary form without thinking about case, but here that dictionary form is exactly what you need because the sentence is saying:

• стека = the modeling tool / palette knife / sculpting tool
• it is the thing that лежит

So the structure is:

• стека = subject
• лежит = verb
• рядом с глиной = location phrase

Yes. Russian very often uses verbs like лежать, стоять, and висеть for the physical position of objects.

So лежит does not only mean that a person is lying down. It can also mean that an object is lying, resting, or located in a horizontal position.

For example:

• Книга лежит на столе. = The book is lying on the table.
• Телефон лежит рядом. = The phone is lying nearby.

In English, we often just say is or is lying, but Russian prefers a more specific positional verb in many everyday situations.

Because рядом с requires the instrumental case.

The base form is:

• глина = clay

But after с in the expression рядом с meaning next to / beside, the noun changes to instrumental:

• глина → глиной

So:

• рядом с глиной = next to the clay

This is a very important pattern:

• рядом с домом = next to the house
• рядом с машиной = next to the car
• рядом с другом = next to a friend

Grammatically, yes — it is the preposition с, which often means with, but in this expression it is part of рядом с, which means next to / beside.

So you should understand рядом с as a fixed combination:

• рядом = nearby / alongside
• рядом с + instrumental = next to something

Do not translate it word by word too mechanically. In this sentence, с is not really best understood as ordinary English with. The whole phrase means beside or next to.

Лежит is:

• 3rd person singular
• present tense
• from the verb лежать = to lie

Its present-tense forms are:

• я лежу
• ты лежишь
• он / она / оно лежит
• мы лежим
• вы лежите
• они лежат

Here the subject стека is singular, so the verb is also singular:

• стека лежит

Yes, you could, and it would be grammatically correct.

But there is a difference in feel:

• стека лежит рядом с глиной sounds natural and concrete: the tool is physically lying there.
• стека находится рядом с глиной is more neutral or formal: the tool is located next to the clay.

In everyday Russian, when the physical position is clear, лежит often sounds more natural than находится.

Yes. Russian word order is more flexible than English word order, because case endings show the grammatical relationships.

The basic version:

• Стeка лежит рядом с глиной.

Other possible orders include:

• Рядом с глиной лежит стека.
• Стeка рядом с глиной лежит.

But the emphasis changes:

• Стeка лежит рядом с глиной. = neutral statement
• Рядом с глиной лежит стека. = emphasis on location, as if answering What is next to the clay?

So not every order is equally natural in every context, even if it is grammatical.

Russian has no articles like the or a/an.

So стека can mean:

• a modeling tool
• the modeling tool

and глиной can mean:

• clay
• the clay
• some clay

The exact meaning depends on context.

That is why the same Russian sentence can be translated into English in different ways depending on the situation.

No, but it is a very common and natural way.

Some alternatives are:

• около глины = near the clay
• возле глины = near/by the clay

These usually take the genitive case, not the instrumental:

• глина → глины

So:

• Стeка лежит около глины.
• Стeка лежит возле глины.

Compared with those, рядом с глиной often feels a bit more like right next to / beside.

Yes. Глиною is also an instrumental singular form of глина.

So both are grammatically correct:

• рядом с глиной
• рядом с глиною

But in modern everyday Russian, глиной is more common and more neutral. The form глиною can sound a bit more literary, poetic, or stylistically marked.

You know from both the noun form and the verb form.

• стека here is singular
• лежит is also singular

If it were plural, you would expect:

• стеки лежат рядом с глиной.

So the verb helps confirm the number:

• singular: лежит
• plural: лежат