Summary

Found nothing out there for the Nexus 5X in terms of nice bumpers for it. Well here you go!
Printed with Ninja - Semi-flex.
Made with Onshape (https://cad.onshape.com/documents/d41aa7947d4a45c403eef770/w/cdb081778b4dcd15109a0791/e/adb412f0a342f69f9861fb23)

I would print it upside down. There's a lip that is best as first layer as the bevel on the bottom layer prevents the need for supports.

Print Settings

Printer Brand:

LulzBot

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>TAZ 5</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>.3 mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>no</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>I used Ninja Semi-Flex @ 218C, no bed heat. </p></div>

Post-Printing

            <p class="detail-caption"><strong>Finished product right off the press.  Very little touchup work is needed (at least not for the Taz5)</strong></p>

Nexus 5x Bumper