This project was built and designed by Rob from Let’s Make Things. Known for creating clever, workshop-friendly jigs, Rob expands his Router Base Onion Build series with a sled that boosts both reach and control when using a router on large workpieces.
This jig is built around a shared plexiglass baseplate used in multiple builds, making it part of a modular router system. Whether you’re flattening slabs or refining large lap joints, this sled offers a level of precision and ease that’s hard to achieve with handheld routing alone.
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Why a Router Sled Is Worth Building
Standard handheld routers are versatile, but their base limits control when working across large surfaces. As you move beyond the diameter of the base, maintaining depth and accuracy becomes a challenge.
Rob solves this with a sled that allows the router to ride smoothly over wide areas. The increased footprint makes the tool more stable, and the platform eliminates unevenness caused by wobble or tilting. It’s an excellent solution for flattening slabs, cutting joints, or even general-purpose routing on oversized workpieces.
Starting with a Flat Base
The core of the sled is a plywood platform that needs to be perfectly flat. Rob uses Baltic birch for its stability, though any flat, quality plywood can work if properly prepped.
To maintain this flatness over time, hardwood braces are added both across and along the platform. These braces help prevent bowing and twisting while also adding structural support to the entire sled.
Installing the Plexiglass Plate
At the center of the system is the shared plexiglass baseplate, which mounts flush into the sled’s plywood top. This shared component allows Rob to move his router between multiple jigs in the series with minimal effort.
The plate is carefully routed into a shallow recess and secured using countersunk screws and bolts. A flush fit is essential for smooth router travel, so care is taken to cut clean edges and test fit before final assembly.
Braces and Build Features
Rob installs cross braces that serve two purposes: structural reinforcement and guiding the router’s movement. These braces are notched and fitted tightly into the sled to hold the platform flat while keeping it rigid during operation.
Handles are added to either end of the sled for easy maneuvering. These are built from hardwood dowels and positioned for balance and comfort. Once glued in place, they provide secure control without getting in the way of the router.
Glue-Up and Flatness Control
To ensure the entire sled remains flat, Rob applies glue to all major joints and clamps the sled down during curing. Weights are added during the drying process to prevent any warping or cupping.
The glue-up is left to dry fully before any finishing touches are added. This careful approach results in a strong, stable platform that performs consistently no matter how many times it’s used.
Using the Sled for Flattening and Joinery
Rob demonstrates the sled in action by flattening a large slab of wood. The router stays level and travels in smooth passes, removing material evenly and producing a flat surface ready for finishing.
For lap joints, Rob first removes the bulk of material using a circular saw and chisel. Then, the sled is used to clean up the recess, producing tight-fitting joints with straight, crisp edges.
Expanding the Jig’s Capability
To expand its reach, Rob installs slotted steel angles along the sled’s edge. These allow the sled to ride on unistrut rails, essentially turning the setup into a full slab-flattening jig with extended range and height control.
Threaded inserts and bolts secure the angles tightly. Additional steps, like chamfering edges and precise drilling, ensure smooth integration with the original sled.
What Sets This Sled Apart
Rob’s sled is part of a modular system, meaning the plexiglass baseplate used here also fits into other jigs like the Router Dog Hole (Onion Build I) and Router Anchor (Onion Build II). This modularity reduces redundancy and expands your workflow without needing a dozen separate tools.
Everything from the counterbored holes to the symmetrical handle placement is done with user comfort and performance in mind. It’s a jig designed not just to work—but to work well over time.
A Worthwhile Upgrade for Any Router
If you do any sort of slab work or need to cut joinery over large surfaces, this router sled is a must-have addition. It bridges the gap between handheld flexibility and the stability of a full router table.
Rob’s attention to detail and smart use of modular design make this build both approachable and highly effective. It’s also adaptable—perfect for anyone wanting to expand what their shop-built jigs can do.
Get Rob’s plans here: https://makethingswithrob.com/make-a-router-sled/.