Me gusta guardar una flor seca en mi cuaderno.

Because gustar works differently from to like in English. A helpful way to think about it is to be pleasing to.

So:

• me = to me
• gusta = is pleasing

That means Me gusta... literally works like ...is pleasing to me.

So instead of saying I like X, Spanish often says X pleases me.

Also, yo gusto is not the normal way to say I like. Yo gusto would mean something more like I am pleasing or I appeal, which is a different idea.

Because the thing that gusta is the whole action guardar una flor seca en mi cuaderno.

After gustar, an infinitive verb like guardar counts as a singular idea, so Spanish uses gusta.

Compare:

• Me gusta leer. = I like reading.
• Me gusta guardar una flor seca... = I like keeping a dried flower...

You use gustan when the thing that is pleasing is a plural noun:

• Me gustan las flores secas.

After gustar, Spanish normally uses the infinitive to talk about liking an activity.

So:

• Me gusta cantar
• Me gusta viajar
• Me gusta guardar una flor seca en mi cuaderno

In English, we often use -ing after like: I like singing, I like travelling.
In Spanish, the usual pattern is gustar + infinitive.

Here guardar means something like to keep, to store, or to put away.

In this sentence, it suggests keeping a dried flower in the notebook, probably between the pages or as a keepsake.

It does not mean to guard in the English sense of protecting something. Even though the words look related, Spanish guardar is broader and often means to keep or to save something.

In Spanish, descriptive adjectives usually come after the noun.

So the normal order is:

• flor seca
• libro interesante
• casa grande

That is why una flor seca is the standard, natural order.

Putting the adjective before the noun is sometimes possible, but it often sounds literary, poetic, or changes the nuance. For an everyday sentence, una flor seca is the expected form.

Because seca has to agree with flor.

Flor is:

• feminine
• singular

So the adjective must also be:

• feminine
• singular

That gives seca.

Compare:

• una flor seca
• un libro seco
• unas flores secas

This is normal adjective agreement in Spanish.

In Spanish, noun gender is not determined only by the ending. While many feminine nouns end in -a, plenty do not.

Flor is simply a feminine noun, so it takes:

• la flor
• una flor

This is something learners often just need to learn noun by noun. The article usually helps you see the gender clearly.

Because Spanish normally does not use an article before a possessive adjective like mi, tu, su, nuestro, etc.

So you say:

• mi cuaderno
• tu casa
• nuestro coche

not:

• el mi cuaderno

The possessive already tells you whose notebook it is, so no article is needed.

En is the natural preposition here because it means in, inside, on, or within, depending on context.

With cuaderno, en mi cuaderno suggests the flower is kept in the notebook, probably between the pages.

Using a would not work here, because a usually indicates movement toward a place or a direct object referring to a person.

You could also say dentro de mi cuaderno if you want to stress inside my notebook, but en mi cuaderno is the normal, simple choice.

It can mean notebook, exercise book, or copybook, depending on context.

In this sentence, notebook is the most natural understanding. It refers to a personal notebook where someone might keep a dried flower.

So cuaderno is a broader word than a very specific English label. Context tells you which English translation fits best.

Yes, but the meaning would change.

• Me gusta guardar una flor seca en mi cuaderno = one dried flower; it feels specific or habitual in a singular way.
• Me gusta guardar flores secas en mi cuaderno = dried flowers in general, possibly more than one.

Both are grammatical. The original sentence focuses on a dried flower as a single object.

Yes, Spanish word order is flexible, but the original order is very natural.

For example, you could also say:

• Me gusta guardar en mi cuaderno una flor seca.

That is still correct, but it shifts the focus slightly toward where the flower is kept.

The original version is straightforward and neutral:

• Me gusta guardar una flor seca en mi cuaderno.

So a learner should treat that as the safest default word order.