Posting below for what I have written so far. It is specific to my case so not really a standard format. Please share if you find a standard format that is absoluetely required by IRCC for this letter.
LETTER OF EXPLANATION
<FULL NAME>
<ADDRESS>
To:
The Visa officer,
IRCC Canada
Subject: Application for an Open Work Permit under the Public Policy Facilitating the Issuance of an Open Work Permit to Former or Current Post-Graduation Work Permit (PGWP) Holders
Respected Sir/Ma’am,
I,
<Name> currently residing in Canada on a post-graduate work permit
(<permit number>, attached below) that is set to expire on the
<expiry of wp date>, am putting forth this application for an open work permit under the public policy that is in effect starting 27th January 2021. I have read the guidelines as part of this policy and understand that I am eligible for a one-time open work permit for upto 18 months. I am thankful for this opportunity and would want to provide some additional information about my current status and history in Canada.
I first landed in Canada in the
<date of first entry> on a study permit and completed my <course and university>. After my graduation, I was granted a
<length> post-graduate work permit in <date>. It was difficult to find work initially due to lockdown and I was hired very late into my one year of eligible period in Canada. I started working as an
<employment details if available>. My contract is attached towards the end of this document. Hence, I request for a timely processing of my application that will allow me to continue working.
<PR Application info if any>I would like to bring to your attention that my Permanent Residence application
(<application number>) is currently under processing, since the
<date of AOR>. Due to COVID the application has not been processed yet and taking longer than usual. I am attaching an acknowledgement of receipt from my PR application below for you reference.
I believe that the information I have provided is adequate and in detail and hope for a positive and favorable consideration of my application.
Yours faithfully,
<Your name>