What is a slip opinion?
<p><a href="https://law.stackexchange.com/a/981/32669">Another answer</a> mentions slip opinions being not yet bound into a volume. Who is it that does this binding, which seems to canonise certain decisions in a certain sense, if only by making them more referable and accessible.</p>
<p>Who makes these decisions of what decisions are worthy of such binding?</p>

<p>All supreme court decisions are bound.  The slip decision merely serves the purpose of making the decision available for reference before the binding has taken place.  See <a href="https://www.supremecourt.gov/opinions/slipopinion/21" rel="nofollow noreferrer">https://www.supremecourt.gov/opinions/slipopinion/21</a> :</p>
<blockquote>
<p>“Slip” opinions are the first version of the Court’s opinions posted on this website. A “slip” opinion consists of the majority or principal opinion, any concurring or dissenting opinions written by the Justices, and a prefatory syllabus prepared by the Reporter’s Office that summarizes the decision. The slip opinions collected here are those issued during October Term 2021 (October 4, 2021, through October 2, 2022). These opinions are posted on the website within minutes after the opinions are issued and will remain posted until the opinions for the entire Term are published in the bound volumes of the United States Reports.</p>
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<p>See also <a href="https://www.supremecourt.gov/opinions/USReports.aspx" rel="nofollow noreferrer">https://www.supremecourt.gov/opinions/USReports.aspx</a> :</p>
<blockquote>
<p>The opinions of the Supreme Court of the United States are published officially in a set of case books called the United States Reports. See 28 U. S. C. §411.</p>
<p>Bound Volumes: The bound volumes of the U. S. Reports are the final generation of the Court’s opinions. See Information About Opinions. The bound volumes of the U. S. Reports collected here contain the full text, from cover through index, of volumes 502 et seq., including all of the opinions, orders, and other materials issued for the Court’s 1991 Term and subsequent years. Additional volumes will be posted here after they are published.</p>
<p>Preliminary Prints: Each bound volume of the U. S. Reports is preceded by “preliminary prints” which are brown, soft-cover “advance pamphlets” that contain the same materials and features of the U. S. Reports. See Information About Opinions. The contents of two or three preliminary prints will eventually be combined into a single bound volume. Thus, the title of each preliminary print includes a part number, e.g., Preliminary Print, Volume 577, Part 1. Prior to publication, all of the materials that go into a preliminary print undergo an extensive editing and indexing process, and permanent page numbers are assigned that will carry over into the bound volume.</p>
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<p>28 USC 411:</p>
<blockquote>
<ol start="411">
<li>Supreme Court reports; printing, binding, and distribution</li>
</ol>
<p>(a) The decisions of the Supreme Court of the United States shall be printed, bound, and distributed in the preliminary prints and bound volumes of the United States Reports as soon as practicable after rendition, to be charged to the proper appropriation for the judiciary. The number and distribution of the copies shall be under the control of the Joint Committee on Printing.</p>
<p>(b) Reports printed prior to June 12, 1926, shall not be furnished the Secretary of the Army, the Secretary of the Navy, or the Secretary of the Air Force.</p>
<p>(c) The Director of the Government Publishing Office, or other printer designated by the Supreme Court of the United States, upon request, shall furnish to the Superintendent of Documents the reports required to be distributed under the provisions of this section.</p>
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united-states common-law precedent