This is my way of making holes. It's probably not the best one, but looks good enough for me.

1. We subdivide a plane one time to many, and select 4 quads for each hole.

2. We do inset. (I)

3. We use Mesh: LoopTools add-on (just enable it) using Cicrcle tool.

(in edit mode right click and then LoopTools->Circle)

4. Inset one more time. (I)

5. Extrude downwards. (E)

6. Add Subdivision Surface modifier

7. Smooth shading (subdivided 2 times)

8. Render Eevee

To make hole sharper you can make more insets.

This is my way of making holes. It's probably not the best one, but looks good enough for me.

1. We subdivide a plane one time to many, and select 4 quads for each hole.

2. We do inset. (I)

3. We use Mesh: LoopTools add-on (just enable it) using Cicrcle tool.

(in edit mode right click and then LoopTools->Circle)

4. Inset one more time. (I)

5. Extrude downwards. (E)

6. Add Subdivision Surface modifier

7. Smooth shading (subdivided 2 times)

8. Render Eevee

To make hole sharper you can make more insets, and extrude down several times to put loop-cuts in all holes.

This is my way of making holes. It's probably not the best one, but looks good enough for me.

1. We subdivide a plane one time to many, and select 4 quads for each hole.

2. We do inset twice. (I)

3. We use Mesh: LoopTools add-on (just enable it) using Cicrcle tool.

(in edit mode right click and then LoopTools->Circle)

4. Extrude downwards. (E)

5. Added Bevel modifier (5 segments)

6. Smooth shading

7.a) Render Eevee

7.b) Render Cycles

The inset sizes are important. To small or to large create artifacts. They need to be just right.

This is my way of making holes. It's probably not the best one, but looks good enough for me.

1. We subdivide a plane one time to many, and select 4 quads for each hole.

2. We do inset. (I)

3. We use Mesh: LoopTools add-on (just enable it) using Cicrcle tool.

(in edit mode right click and then LoopTools->Circle)

4. Inset one more time. (I)

5. Extrude downwards. (E)

6. Add Subdivision Surface modifier

7. Smooth shading (subdivided 2 times)

8. Render Eevee

To make hole sharper you can make more insets.