ADVICE NEEDED: Thickness and surfacing short boards?

Do you have a planer? You can hotglue pieces to a longer flat piece of sheet goods. Make sure they are adhered well before running them through and take light cuts.

Can be done with handtools as well, but I do not have the experience to offer any advice with that.

Drum sander would be safer. This is how to sand short pieces. Take a larger piece, at least the min. length to be safe to run under the sander and a little wider than the piece you want to sand. Lay your piece on top of larger piece and attach small pieces around the smaller piece. The pieces around the smaller piece need to be below the thickness of the piece to be sanded. Set sander to height of the piece to sand. Make sure the pieces around the piece you want to sand are snug up to the piece you want to sand. This will hold the piece to be sanded while the sander does it thing. You might need to turn off sander to remove piece after it is sanded. It may even work if you put several pieces together that you want to sand and secure with pieces on sides. I have had a piece of wood shoot back out of my drum sander, so be sure and stand to the side when guiding the pieces into your sander. In my last garage shop, I had a an upright freezer right behind my table saw. It got my second piece of wood that shot back. My stomach got the first. Had a bruise the size of a soccer ball for about a week. Lesson learned. I now stand slightly to the side of every tool that might shoot back. Good luck.

Hand plane and a thicknessing jig

-- https://www.jtplaneworks.com - In theory, there is no difference between theory and practice. In practice, there is.

You should be able to run small boards through a drum sander, though without a sled or some other solution a thickness planer is not an option.

Why would a drum sander not work with say a 12” board?

Go to YouTube, lots of ways to skin that cat

https://youtu.be/xIJoQ2v-wdM

https://youtu.be/XnfMAL8BwTA

https://youtu.be/lJF00qxcayg

Edit to add: video #1 Save a bunch of time by running 2 parallel strips of double sticky tape down the carrier board then just stick your pieces to it. No need to cut and stick 2 pieces tape for each piece of stock individually

-- Alaskan's for Global warming!

Hi
I have no stand up machines just hand held power tools including a router. I thickness using a hand held router.
You can see how I do it on part 2 of my blog here http://lumberjocks.com/anthm27/blog/128793
See Paragraph 3 and pics 2 and 3
Hope that helps.
Kind Regards
Anth

-- There is no hope for any of us if we keep apologizing for telling the truth.

My method is similar to what has been suggested above. I would start by grouping pieces of similar width and then trim them so that they are all the same width within each group. Do this very carefully as they are even quite small to be run through a table saw. Once this is done, put them end to end to create groupings of 3 to 4 feet in length and then hot melt glue narrow waste strips (3/4” width works OK) to each side extending beyond each end by about 6”. These sacrificial waste strips should be about equal to the thickest piece in the grouping. This holds all the pieces together and the extended ends prevents snipe (if you are using a thickness planner). Check with your shared workshop to see if they would allow this configuration to be run through the planner. Once you have everything to the thickness you want, run the groups through the table saw again to rip off the sacrificial strips.