Wooden Stools

It comprises a flat, horizontal surface whichthat is made up of a variety of materials, including metal, plastic, plywood, or wood, which I prefer most often.

The surface couldan be supported by three or four legs, however, I generally build only for four, because it's a bit difficult for me to make the stool with three legs.

The legs are also made bywith wood.

When attaching the legs to the surface, I use screws and some fasteners, (as/because) they are more efficient than the traditional mortise- and tenon joint structures.

Almost no one will know what a mortise and tenon joint is, so I recommend using "interlocking wood joints, like the traditional mortise and tenon joint structures" instead.

It is true that the traditional method is profoundly stable and strong, and is able to support heavy loadings, whereas it costs a lot of times, but it takes a lot of time (to make / to construct).

Therefore, in most cases, I do not use this waymethod to join (two separate) pieces.

It comprises a flat, horizontal surface which made up of a variety of materials, including metal, plastic, plywood, or wood, which I prefer often.

It entails creating a flat, horizontal seat from a chosen material, such as metal, plastic, plywood, or wood, the latter which I prefer the most.

The surface could be supported by three or four legs, however, I generally build only for four, because it's a bit difficult for me to make the stool with three legs.

The seat can be supported by three or four legs; however, I generally only build with four, because it's a bit more difficult for me to make three-legged stools.

The legs are also made by wood.

The legs are also made out of wood.

When attaching the legs to the surface, I use screws and some fasteners, they are more efficient than the traditional mortise-tenon joint structures.

When attaching the legs to the surface, I use screws and some fasteners. I find that they are more efficient than the traditional mortise-tenon joint structures.

It is true that the traditional method is profoundly stable and strong, and is able to support heavy loadings, whereas it costs a lot of time.

While the traditional method is significantly more stable and able to support heavier loadings, it requires a lot of time.

Wooden Stools

ItA stool comprises a flat, horizontal surface which made up of a variety of materials, including metal, plastic, plywood, or wood, [which I prefer often], and some legs.

“Which I prefer often” appears to modify all four materials. Is this what you mean?

It [comprises] a top AND some legs.

I wouldn’t consider a stool with a metal or plastic top to be a “wooden” stool.

The surface could be supported by three or four legs, however, I generally build (only for) four, because it's a bit difficult for me to make thea stool with three legs.

The legs are also made byof wood.

They are made OF wood BY you.

When attaching the legs to the surface, I use screws and some fasteners, theywhich are more efficient than the traditional mortise-and-tenon joint structures.

It is true that the traditional method is profoundly stable and strong, and is able to support heavy loadings, whereas it costs, but it takes a lot of time.