Please make sure that you use present simple/indefinite tense in this type of question. Also, have a good command over passive voice for the same tense. This vocabulary will help you:

Introduction

The diagram/picture/flow chart depicts/illustrates/describes the process of ___________/ how ____________ .

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While describing the process:

First/Firstly, second/secondly, third/thirdly, next, after that, then, following that, followed by, subsequently, subsequent to that, finally, lastly

where, from where, after which, after that, afterwards

when, as soon as, immediately, just after that

at the beginning, in the end, just after the beginning, just before the end

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To denote the end of a step:

after this step/stage/process

once this stage/step is completed/over

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To denote what a step involves:

The phase/step/stage involves

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To denote the repetition of a cycle/process

The cycle/process then repeats itself

The cycle/process is then repeated.

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