The following instructions are compiled from multiple Esri online help topics, to hopefully facilitate this process! Following are instructions for doing this in ArcGIS Online, but it can also be done in Pro, if preferred.

Here is a really nice Storymap which details the process!

Enabling layers and maps for offline use

To take a web map offline, all the layers, including the basemap and reference layers, must be enabled for offline use. Esri raster basemaps and Esri vector basemaps are automatically enabled for offline use. You can enable the following additional types of map layers for offline use: 

  • Hosted feature layers
  • ArcGIS Server feature layers
  • Hosted tile layers
  • ArcGIS Server cached map services (also called tile layers)—Check the Allow clients to export cache tiles check box when you publish the service from ArcGIS Pro.
  • ArcGIS Server cached image services (also called imagery layers)—Check the Allow clients to export cache tiles check box when you publish the service from ArcGIS Pro.
  • Sketch layers and map note layers* saved in the web map
Note:

*Map note layers that you save as  feature collection items and add to a map cannot be taken offline.

Create the Basemap

  1. Select a (non-deprecated) Esri basemap from Esri raster basemaps or Esri vector basemaps
  2. Click the ... icon in the bottom right corner and choose to Open in Map Viewer
  3. If you choose to add additional layers or another basemap, do so now. NOTE: Add an additional basemap as a Layer, not a Basemap.
  4. Once you have added the desired layers to the map, Save it. NOTE: If this option is not available to you, make sure you are logged into ArcGIS Online (top right corner).
  5. From the Map Properties icon, select Item Details
  6. Within the Item Details, go to the Settings.
  7. Within Settings, choose Offline and verify that Enable offline mode is indicated
  8. Next, Manage Offline Areas to create specific areas of the offline map to make download and use easier and quicker. (see image above)
  9. Within Manage Offline Areas, click Create offline area.
  10. Using the draw tools within the Map, define the Map Area and set the configurations, as appropriate before clicking Save.
  11. The Map Areas will indicate that it is packing. Once done, the Packaging indicator will disappear. The time required to package the map area differs according to the layers and size of the area.
  12. Create up to 16 Map Areas, as needed.
  13. Close the Manage Offline Areas by clicking the X in the top right corner.
  14. Scroll to the top of Settings and navigate to the Overview section.
  15. Within Overview, Share the Web Map to the appropriate audience and Save the changes.
  16. In Survey123 Connect, select the survey to which to add the Basemap.
  17. Navigate to the Linked Content section and + Link content.
  18. Within Linked Content, choose Online Map and then select the newly created Web Map and click OK.
  19. Navigate to the survey Form, and click on the Map within your location question.
  20. Click the basemap icon and click the newly added basemap to verify that it works properly.

  21. Publish the survey so that the new basemap is available for use.

Congratulations, you've created the offline basemap and linked it to the survey so it can now be used! See the Use offline basemaps solution for instructions on how to use it within the Survey123 app.