هذه الطريقة سهلة.

A careful MSA pronunciation is:

hādhihi aṭ-ṭarīqatu sahlatun

In everyday careful speech without full case endings, you will often hear something closer to:

hādhihi aṭ-ṭarīqa sahlah

A few useful pronunciation notes:

• هذه = hādhihi
• الطريقة is pronounced aṭ-ṭarīqa, not al-ṭarīqa
• سهلة is sahla or sahlah

If you are not yet learning case endings in detail, hādhihi aṭ-ṭarīqa سهلة with simple pause pronunciation is a good practical target.

Because Arabic often leaves out the present-tense to be.

So:

• هذه الطريقة سهلة = This method is easy

There is no separate word for is in the present tense in normal Arabic nominal sentences.

But in the past or future, Arabic does use a verb:

• كانت هذه الطريقة سهلة = This method was easy
• ستكون هذه الطريقة سهلة = This method will be easy

So the missing is is completely normal here.

Because طريقة is a feminine singular noun.

In Arabic, demonstratives must agree with the noun:

• هذا = this for masculine singular
• هذه = this for feminine singular

Since طريقة is feminine, you say:

• هذه الطريقة

not

• هذا الطريقة

It is grammatically feminine, and one big clue is the ending ة (called tāʾ marbūṭa).

Many Arabic nouns ending in ة are feminine, including:

• طريقة = method
• سيارة = car
• لغة = language

So because طريقة is feminine, anything that agrees with it also becomes feminine, such as:

• the demonstrative: هذه
• the adjective: سهلة

In MSA, when a demonstrative like هذه comes before a noun, the noun is usually also definite with ال.

So the normal pattern is:

• هذا الكتاب = this book
• هذه الطريقة = this method

That is just how standard Arabic structures this kind of phrase.

If you remove ال and say هذه طريقة سهلة, that usually has a slightly different feel, more like:

• This is an easy method
• This is an easy way

So:

• هذه الطريقة سهلة = This method is easy
• هذه طريقة سهلة = This is an easy method

Because ط is a sun letter.

With sun letters, the ل of ال is not pronounced separately. Instead, the next consonant is doubled.

So:

• written: الطريقة
• pronounced: aṭ-ṭarīqa

This happens with all sun letters, for example:

• الشمس → ash-shams
• الطريق → aṭ-ṭarīq
• النور → an-nūr

So the spelling keeps ال, but the pronunciation changes.

Because in Arabic, adjectives normally follow the noun they describe.

So:

• الطريقة السهلة = the easy method
• noun first, adjective second

In your sentence:

• هذه الطريقة سهلة

the adjective سهلة still comes after the noun الطريقة.

This is different from English, where adjectives usually come before the noun, as in easy method.

Because adjectives agree with the noun in gender and number.

Since طريقة is feminine singular, the adjective must also be feminine singular:

• masculine: سهل
• feminine: سهلة

So:

• الكتاب سهل = the book is easy
• الطريقة سهلة = the method is easy

This agreement is very important in Arabic.

Because here سهلة is the predicate of the sentence, not an adjective inside a noun phrase.

Compare these two:

1. هذه الطريقة سهلة

   • This method is easy
   • Here سهلة is the predicate, so it is normally indefinite

2. هذه الطريقة السهلة

   • this easy method
   • Here السهلة is an adjective directly modifying الطريقة, so it matches it in definiteness

This is a very common Arabic pattern:

• البيت كبير = the house is big
• البيت الكبير = the big house

So in your sentence, سهلة is correct because the sentence means is easy, not the easy method.

That ة is called tāʾ marbūṭa.

It usually marks feminine nouns and adjectives. In this sentence:

• طريقة is feminine because of ة
• سهلة is the feminine form of سهل

In pronunciation:

• at pause, it usually sounds like -a or -ah
• when full grammatical endings are pronounced, it can sound like t

So with full case endings:

• الطريقةُ = aṭ-ṭarīqatu
• سهلةٌ = sahlatun

But when pausing in normal speech, learners often hear:

• aṭ-ṭarīqa
• sahla

A fully vowelled version is:

هٰذِهِ الطَّرِيقَةُ سَهْلَةٌ

This shows the basic grammatical endings:

• هٰذِهِ
• الطَّرِيقَةُ = nominative, because it is the subject/topic of the nominal sentence
• سَهْلَةٌ = nominative predicate

Many texts for learners omit these endings, so you often see simply:

هذه الطريقة سهلة

Both are normal; the second is just less fully marked.